Ubuntu Manpage: tor - The second-generation onion router

NAME

       tor - The second-generation onion router

SYNOPSIS

       tor [OPTION value]...

DESCRIPTION

       Tor is a connection-oriented anonymizing communication service. Users choose a source-routed path through
       a set of nodes, and negotiate a "virtual circuit" through the network, in which each node knows its
       predecessor and successor, but no others. Traffic flowing down the circuit is unwrapped by a symmetric
       key at each node, which reveals the downstream node.

       Basically, Tor provides a distributed network of servers or relays ("onion routers"). Users bounce their
       TCP streams — web traffic, ftp, ssh, etc. — around the network, and recipients, observers, and even the
       relays themselves have difficulty tracking the source of the stream.

       By default, tor will act as a client only. To help the network by providing bandwidth as a relay, change
       the ORPort configuration option — see below. Please also consult the documentation on the Tor Project’s
       website.

COMMAND-LINE OPTIONS

-h, -help
Display a short help message and exit.

-f FILE
Specify a new configuration file to contain further Tor configuration options OR pass - to make Tor
read its configuration from standard input. (Default: /etc/tor/torrc, or $HOME/.torrc if that file is
not found)

--allow-missing-torrc
Do not require that configuration file specified by -f exist if default torrc can be accessed.

--defaults-torrc FILE
Specify a file in which to find default values for Tor options. The contents of this file are
overridden by those in the regular configuration file, and by those on the command line. (Default:
/etc/tor/torrc-defaults.)

--ignore-missing-torrc
Specifies that Tor should treat a missing torrc file as though it were empty. Ordinarily, Tor does
this for missing default torrc files, but not for those specified on the command line.

--hash-password PASSWORD
Generates a hashed password for control port access.

--list-fingerprint
Generate your keys and output your nickname and fingerprint.

--verify-config
Verify the configuration file is valid.

--service install [--options command-line options]
Install an instance of Tor as a Windows service, with the provided command-line options. Current
instructions can be found at https://www.torproject.org/docs/faq#NTService

--service remove|start|stop
Remove, start, or stop a configured Tor Windows service.

--nt-service
Used internally to implement a Windows service.

--list-torrc-options
List all valid options.

--list-deprecated-options
List all valid options that are scheduled to become obsolete in a future version. (This is a warning,
not a promise.)

--version
Display Tor version and exit.

--quiet|--hush
Override the default console log. By default, Tor starts out logging messages at level "notice" and
higher to the console. It stops doing so after it parses its configuration, if the configuration
tells it to log anywhere else. You can override this behavior with the --hush option, which tells Tor
to only send warnings and errors to the console, or with the --quiet option, which tells Tor not to
log to the console at all.

--keygen [--newpass]
Running "tor --keygen" creates a new ed25519 master identity key for a relay, or only a fresh
temporary signing key and certificate, if you already have a master key. Optionally you can encrypt
the master identity key with a passphrase: Tor will ask you for one. If you don’t want to encrypt the
master key, just don’t enter any passphrase when asked.

The --newpass option should be used with --keygen only when you need to add, change, or remove a
passphrase on an existing ed25519 master identity key. You will be prompted for the old passphase (if
any), and the new passphrase (if any).

When generating a master key, you will probably want to use --DataDirectory to control where the keys
and certificates will be stored, and --SigningKeyLifetime to control their lifetimes. Their behavior
is as documented in the server options section below. (You must have write access to the specified
DataDirectory.)

To use the generated files, you must copy them to the DataDirectory/keys directory of your Tor
daemon, and make sure that they are owned by the user actually running the Tor daemon on your system.

--passphrase-fd FILEDES
Filedescriptor to read the passphrase from. Note that unlike with the tor-gencert program, the entire
file contents are read and used as the passphrase, including any trailing newlines. Default: read
from the terminal.

--key-expiration [purpose]
The purpose specifies which type of key certificate to determine the expiration of. The only
currently recognised purpose is "sign".

Running "tor --key-expiration sign" will attempt to find your signing key certificate and will
output, both in the logs as well as to stdout, the signing key certificate’s expiration time in
ISO-8601 format. For example, the output sent to stdout will be of the form: "signing-cert-expiry:
2017-07-25 08:30:15 UTC"

Other options can be specified on the command-line in the format "--option value", in the format "option
value", or in a configuration file. For instance, you can tell Tor to start listening for SOCKS
connections on port 9999 by passing --SocksPort 9999 or SocksPort 9999 to it on the command line, or by
putting "SocksPort 9999" in the configuration file. You will need to quote options with spaces in them:
if you want Tor to log all debugging messages to debug.log, you will probably need to say --Log debug
file debug.log.

Options on the command line override those in configuration files. See the next section for more
information.

THE CONFIGURATION FILE FORMAT

All configuration options in a configuration are written on a single line by default. They take the form
of an option name and a value, or an option name and a quoted value (option value or option "value").
Anything after a # character is treated as a comment. Options are case-insensitive. C-style escaped
characters are allowed inside quoted values. To split one configuration entry into multiple lines, use a
single backslash character (\) before the end of the line. Comments can be used in such multiline
entries, but they must start at the beginning of a line.

Configuration options can be imported from files or folders using the %include option with the value
being a path. If the path is a file, the options from the file will be parsed as if they were written
where the %include option is. If the path is a folder, all files on that folder will be parsed following
lexical order. Files starting with a dot are ignored. Files on subfolders are ignored. The %include
option can be used recursively.

By default, an option on the command line overrides an option found in the configuration file, and an
option in a configuration file overrides one in the defaults file.

This rule is simple for options that take a single value, but it can become complicated for options that
are allowed to occur more than once: if you specify four SocksPorts in your configuration file, and one
more SocksPort on the command line, the option on the command line will replace all of the SocksPorts in
the configuration file. If this isn’t what you want, prefix the option name with a plus sign (+), and it
will be appended to the previous set of options instead. For example, setting SocksPort 9100 will use
only port 9100, but setting +SocksPort 9100 will use ports 9100 and 9050 (because this is the default).

Alternatively, you might want to remove every instance of an option in the configuration file, and not
replace it at all: you might want to say on the command line that you want no SocksPorts at all. To do
that, prefix the option name with a forward slash (/). You can use the plus sign (+) and the forward
slash (/) in the configuration file and on the command line.

GENERAL OPTIONS

BandwidthRate N bytes|KBytes|MBytes|GBytes|TBytes|KBits|MBits|GBits|TBits
A token bucket limits the average incoming bandwidth usage on this node to the specified number of
bytes per second, and the average outgoing bandwidth usage to that same value. If you want to run a
relay in the public network, this needs to be at the very least 75 KBytes for a relay (that is, 600
kbits) or 50 KBytes for a bridge (400 kbits) — but of course, more is better; we recommend at least
250 KBytes (2 mbits) if possible. (Default: 1 GByte)

Note that this option, and other bandwidth-limiting options, apply to TCP data only: They do not
count TCP headers or DNS traffic.

With this option, and in other options that take arguments in bytes, KBytes, and so on, other formats
are also supported. Notably, "KBytes" can also be written as "kilobytes" or "kb"; "MBytes" can be
written as "megabytes" or "MB"; "kbits" can be written as "kilobits"; and so forth. Tor also accepts
"byte" and "bit" in the singular. The prefixes "tera" and "T" are also recognized. If no units are
given, we default to bytes. To avoid confusion, we recommend writing "bytes" or "bits" explicitly,
since it’s easy to forget that "B" means bytes, not bits.

MaxAdvertisedBandwidth N bytes|KBytes|MBytes|GBytes|TBytes|KBits|MBits|GBits|TBits
If set, we will not advertise more than this amount of bandwidth for our BandwidthRate. Server
operators who want to reduce the number of clients who ask to build circuits through them (since this
is proportional to advertised bandwidth rate) can thus reduce the CPU demands on their server without
impacting network performance.

RelayBandwidthRate N bytes|KBytes|MBytes|GBytes|TBytes|KBits|MBits|GBits|TBits
If not 0, a separate token bucket limits the average incoming bandwidth usage for _relayed traffic_
on this node to the specified number of bytes per second, and the average outgoing bandwidth usage to
that same value. Relayed traffic currently is calculated to include answers to directory requests,
but that may change in future versions. (Default: 0)

ClientTransportPlugin transport socks4|socks5 IP:PORT, ClientTransportPlugin transport exec
path-to-binary [options]
In its first form, when set along with a corresponding Bridge line, the Tor client forwards its
traffic to a SOCKS-speaking proxy on "IP:PORT". (IPv4 addresses should written as-is; IPv6 addresses
should be wrapped in square brackets.) It’s the duty of that proxy to properly forward the traffic to
the bridge.

In its second form, when set along with a corresponding Bridge line, the Tor client launches the
pluggable transport proxy executable in path-to-binary using options as its command-line options, and
forwards its traffic to it. It’s the duty of that proxy to properly forward the traffic to the
bridge.

ServerTransportPlugin transport exec path-to-binary [options]
The Tor relay launches the pluggable transport proxy in path-to-binary using options as its
command-line options, and expects to receive proxied client traffic from it.

ServerTransportListenAddr transport IP:PORT
When this option is set, Tor will suggest IP:PORT as the listening address of any pluggable transport
proxy that tries to launch transport. (IPv4 addresses should written as-is; IPv6 addresses should be
wrapped in square brackets.)

ServerTransportOptions transport k=v k=v ...
When this option is set, Tor will pass the k=v parameters to any pluggable transport proxy that tries
to launch transport.

(Example: ServerTransportOptions obfs45 shared-secret=bridgepasswd cache=/var/lib/tor/cache)

ExtORPort [address:]port|auto
Open this port to listen for Extended ORPort connections from your pluggable transports.

ExtORPortCookieAuthFile Path
If set, this option overrides the default location and file name for the Extended ORPort’s cookie
file — the cookie file is needed for pluggable transports to communicate through the Extended ORPort.

ExtORPortCookieAuthFileGroupReadable 0|1
If this option is set to 0, don’t allow the filesystem group to read the Extended OR Port cookie
file. If the option is set to 1, make the cookie file readable by the default GID. [Making the file
readable by other groups is not yet implemented; let us know if you need this for some reason.]
(Default: 0)

ConnLimit NUM
The minimum number of file descriptors that must be available to the Tor process before it will
start. Tor will ask the OS for as many file descriptors as the OS will allow (you can find this by
"ulimit -H -n"). If this number is less than ConnLimit, then Tor will refuse to start.

You probably don’t need to adjust this. It has no effect on Windows since that platform lacks
getrlimit(). (Default: 1000)

DisableNetwork 0|1
When this option is set, we don’t listen for or accept any connections other than controller
connections, and we close (and don’t reattempt) any outbound connections. Controllers sometimes use
this option to avoid using the network until Tor is fully configured. (Default: 0)

ConstrainedSockets 0|1
If set, Tor will tell the kernel to attempt to shrink the buffers for all sockets to the size
specified in ConstrainedSockSize. This is useful for virtual servers and other environments where
system level TCP buffers may be limited. If you’re on a virtual server, and you encounter the "Error
creating network socket: No buffer space available" message, you are likely experiencing this
problem.

The preferred solution is to have the admin increase the buffer pool for the host itself via
/proc/sys/net/ipv4/tcp_mem or equivalent facility; this configuration option is a second-resort.

The DirPort option should also not be used if TCP buffers are scarce. The cached directory requests
consume additional sockets which exacerbates the problem.

You should not enable this feature unless you encounter the "no buffer space available" issue.
Reducing the TCP buffers affects window size for the TCP stream and will reduce throughput in
proportion to round trip time on long paths. (Default: 0)

ConstrainedSockSize N bytes|KBytes
When ConstrainedSockets is enabled the receive and transmit buffers for all sockets will be set to
this limit. Must be a value between 2048 and 262144, in 1024 byte increments. Default of 8192 is
recommended.

ControlPort PORT|unix:path|auto [flags]
If set, Tor will accept connections on this port and allow those connections to control the Tor
process using the Tor Control Protocol (described in control-spec.txt in torspec). Note: unless you
also specify one or more of HashedControlPassword or CookieAuthentication, setting this option will
cause Tor to allow any process on the local host to control it. (Setting both authentication methods
means either method is sufficient to authenticate to Tor.) This option is required for many Tor
controllers; most use the value of 9051. If a unix domain socket is used, you may quote the path
using standard C escape sequences. Set it to "auto" to have Tor pick a port for you. (Default: 0)

Recognized flags are...

GroupWritable
Unix domain sockets only: makes the socket get created as group-writable.

WorldWritable
Unix domain sockets only: makes the socket get created as world-writable.

RelaxDirModeCheck
Unix domain sockets only: Do not insist that the directory that holds the socket be
read-restricted.

ControlSocket Path
Like ControlPort, but listens on a Unix domain socket, rather than a TCP socket. 0 disables
ControlSocket (Unix and Unix-like systems only.)

ControlSocketsGroupWritable 0|1
If this option is set to 0, don’t allow the filesystem group to read and write unix sockets (e.g.
ControlSocket). If the option is set to 1, make the control socket readable and writable by the
default GID. (Default: 0)

HashedControlPassword hashed_password
Allow connections on the control port if they present the password whose one-way hash is
hashed_password. You can compute the hash of a password by running "tor --hash-password password".
You can provide several acceptable passwords by using more than one HashedControlPassword line.

CookieAuthentication 0|1
If this option is set to 1, allow connections on the control port when the connecting process knows
the contents of a file named "control_auth_cookie", which Tor will create in its data directory. This
authentication method should only be used on systems with good filesystem security. (Default: 0)

CookieAuthFile Path
If set, this option overrides the default location and file name for Tor’s cookie file. (See
CookieAuthentication above.)

CookieAuthFileGroupReadable 0|1
If this option is set to 0, don’t allow the filesystem group to read the cookie file. If the option
is set to 1, make the cookie file readable by the default GID. [Making the file readable by other
groups is not yet implemented; let us know if you need this for some reason.] (Default: 0)

ControlPortWriteToFile Path
If set, Tor writes the address and port of any control port it opens to this address. Usable by
controllers to learn the actual control port when ControlPort is set to "auto".

ControlPortFileGroupReadable 0|1
If this option is set to 0, don’t allow the filesystem group to read the control port file. If the
option is set to 1, make the control port file readable by the default GID. (Default: 0)

DataDirectory DIR
Store working data in DIR. Can not be changed while tor is running. (Default: ~/.tor if your home
directory is not /; otherwise, /var/lib/tor. On Windows, the default is your ApplicationData folder.)

DataDirectoryGroupReadable 0|1
If this option is set to 0, don’t allow the filesystem group to read the DataDirectory. If the option
is set to 1, make the DataDirectory readable by the default GID. (Default: 0)

FallbackDir ipv4address:port orport=port id=fingerprint [weight=num] [ipv6=[ipv6address]:orport]
When we’re unable to connect to any directory cache for directory info (usually because we don’t know
about any yet) we try a directory authority. Clients also simultaneously try a FallbackDir, to avoid
hangs on client startup if a directory authority is down. Clients retry FallbackDirs more often than
directory authorities, to reduce the load on the directory authorities. By default, the directory
authorities are also FallbackDirs. Specifying a FallbackDir replaces Tor’s default hard-coded
FallbackDirs (if any). (See the DirAuthority entry for an explanation of each flag.)

UseDefaultFallbackDirs 0|1
Use Tor’s default hard-coded FallbackDirs (if any). (When a FallbackDir line is present, it replaces
the hard-coded FallbackDirs, regardless of the value of UseDefaultFallbackDirs.) (Default: 1)

DirAuthority [nickname] [flags] ipv4address:port fingerprint
Use a nonstandard authoritative directory server at the provided address and port, with the specified
key fingerprint. This option can be repeated many times, for multiple authoritative directory
servers. Flags are separated by spaces, and determine what kind of an authority this directory is. By
default, an authority is not authoritative for any directory style or version unless an appropriate
flag is given. Tor will use this authority as a bridge authoritative directory if the "bridge" flag
is set. If a flag "orport=port" is given, Tor will use the given port when opening encrypted tunnels
to the dirserver. If a flag "weight=num" is given, then the directory server is chosen randomly with
probability proportional to that weight (default 1.0). If a flag "v3ident=fp" is given, the dirserver
is a v3 directory authority whose v3 long-term signing key has the fingerprint fp. Lastly, if an
"ipv6=[ipv6address]:orport" flag is present, then the directory authority is listening for IPv6
connections on the indicated IPv6 address and OR Port.

Tor will contact the authority at ipv4address to download directory documents. The provided port
value is a dirport; clients ignore this in favor of the specified "orport=" value. If an IPv6 ORPort
is supplied, Tor will also download directory documents at the IPv6 ORPort.

If no DirAuthority line is given, Tor will use the default directory authorities. NOTE: this option
is intended for setting up a private Tor network with its own directory authorities. If you use it,
you will be distinguishable from other users, because you won’t believe the same authorities they do.

DirAuthorityFallbackRate NUM
When configured to use both directory authorities and fallback directories, the directory authorities
also work as fallbacks. They are chosen with their regular weights, multiplied by this number, which
should be 1.0 or less. The default is less than 1, to reduce load on authorities. (Default: 0.1)

AlternateDirAuthority [nickname] [flags] ipv4address:port fingerprint

AlternateBridgeAuthority [nickname] [flags] ipv4address:port fingerprint
These options behave as DirAuthority, but they replace fewer of the default directory authorities.
Using AlternateDirAuthority replaces the default Tor directory authorities, but leaves the default
bridge authorities in place. Similarly, AlternateBridgeAuthority replaces the default bridge
authority, but leaves the directory authorities alone.

DisableAllSwap 0|1
If set to 1, Tor will attempt to lock all current and future memory pages, so that memory cannot be
paged out. Windows, OS X and Solaris are currently not supported. We believe that this feature works
on modern Gnu/Linux distributions, and that it should work on *BSD systems (untested). This option
requires that you start your Tor as root, and you should use the User option to properly reduce Tor’s
privileges. Can not be changed while tor is running. (Default: 0)

DisableDebuggerAttachment 0|1
If set to 1, Tor will attempt to prevent basic debugging attachment attempts by other processes. This
may also keep Tor from generating core files if it crashes. It has no impact for users who wish to
attach if they have CAP_SYS_PTRACE or if they are root. We believe that this feature works on modern
Gnu/Linux distributions, and that it may also work on *BSD systems (untested). Some modern Gnu/Linux
systems such as Ubuntu have the kernel.yama.ptrace_scope sysctl and by default enable it as an
attempt to limit the PTRACE scope for all user processes by default. This feature will attempt to
limit the PTRACE scope for Tor specifically - it will not attempt to alter the system wide ptrace
scope as it may not even exist. If you wish to attach to Tor with a debugger such as gdb or strace
you will want to set this to 0 for the duration of your debugging. Normal users should leave it on.
Disabling this option while Tor is running is prohibited. (Default: 1)

FetchDirInfoEarly 0|1
If set to 1, Tor will always fetch directory information like other directory caches, even if you
don’t meet the normal criteria for fetching early. Normal users should leave it off. (Default: 0)

FetchDirInfoExtraEarly 0|1
If set to 1, Tor will fetch directory information before other directory caches. It will attempt to
download directory information closer to the start of the consensus period. Normal users should leave
it off. (Default: 0)

FetchHidServDescriptors 0|1
If set to 0, Tor will never fetch any hidden service descriptors from the rendezvous directories.
This option is only useful if you’re using a Tor controller that handles hidden service fetches for
you. (Default: 1)

FetchServerDescriptors 0|1
If set to 0, Tor will never fetch any network status summaries or server descriptors from the
directory servers. This option is only useful if you’re using a Tor controller that handles directory
fetches for you. (Default: 1)

FetchUselessDescriptors 0|1
If set to 1, Tor will fetch every consensus flavor, descriptor, and certificate that it hears about.
Otherwise, it will avoid fetching useless descriptors: flavors that it is not using to build
circuits, and authority certificates it does not trust. This option is useful if you’re using a tor
client with an external parser that uses a full consensus. This option fetches all documents,
DirCache fetches and serves all documents. (Default: 0)

HTTPProxy host[:port]
Tor will make all its directory requests through this host:port (or host:80 if port is not
specified), rather than connecting directly to any directory servers. (DEPRECATED: As of
0.3.1.0-alpha you should use HTTPSProxy.)

HTTPProxyAuthenticator username:password
If defined, Tor will use this username:password for Basic HTTP proxy authentication, as in RFC 2617.
This is currently the only form of HTTP proxy authentication that Tor supports; feel free to submit a
patch if you want it to support others. (DEPRECATED: As of 0.3.1.0-alpha you should use
HTTPSProxyAuthenticator.)

HTTPSProxy host[:port]
Tor will make all its OR (SSL) connections through this host:port (or host:443 if port is not
specified), via HTTP CONNECT rather than connecting directly to servers. You may want to set
FascistFirewall to restrict the set of ports you might try to connect to, if your HTTPS proxy only
allows connecting to certain ports.

HTTPSProxyAuthenticator username:password
If defined, Tor will use this username:password for Basic HTTPS proxy authentication, as in RFC 2617.
This is currently the only form of HTTPS proxy authentication that Tor supports; feel free to submit
a patch if you want it to support others.

Sandbox 0|1
If set to 1, Tor will run securely through the use of a syscall sandbox. Otherwise the sandbox will
be disabled. The option is currently an experimental feature. It only works on Linux-based operating
systems, and only when Tor has been built with the libseccomp library. This option can not be changed
while tor is running.

When the Sandbox is 1, the following options can not be changed when tor is running: Address
ConnLimit CookieAuthFile DirPortFrontPage ExtORPortCookieAuthFile Logs ServerDNSResolvConfFile Tor
must remain in client or server mode (some changes to ClientOnly and ORPort are not allowed).
(Default: 0)

Socks4Proxy host[:port]
Tor will make all OR connections through the SOCKS 4 proxy at host:port (or host:1080 if port is not
specified).

Socks5Proxy host[:port]
Tor will make all OR connections through the SOCKS 5 proxy at host:port (or host:1080 if port is not
specified).

Socks5ProxyUsername username

Socks5ProxyPassword password
If defined, authenticate to the SOCKS 5 server using username and password in accordance to RFC 1929.
Both username and password must be between 1 and 255 characters.

SocksSocketsGroupWritable 0|1
If this option is set to 0, don’t allow the filesystem group to read and write unix sockets (e.g.
SocksSocket). If the option is set to 1, make the SocksSocket socket readable and writable by the
default GID. (Default: 0)

KeepalivePeriod NUM
To keep firewalls from expiring connections, send a padding keepalive cell every NUM seconds on open
connections that are in use. If the connection has no open circuits, it will instead be closed after
NUM seconds of idleness. (Default: 5 minutes)

Log minSeverity[-maxSeverity] stderr|stdout|syslog
Send all messages between minSeverity and maxSeverity to the standard output stream, the standard
error stream, or to the system log. (The "syslog" value is only supported on Unix.) Recognized
severity levels are debug, info, notice, warn, and err. We advise using "notice" in most cases, since
anything more verbose may provide sensitive information to an attacker who obtains the logs. If only
one severity level is given, all messages of that level or higher will be sent to the listed
destination.

Log minSeverity[-maxSeverity] file FILENAME
As above, but send log messages to the listed filename. The "Log" option may appear more than once in
a configuration file. Messages are sent to all the logs that match their severity level.

Log [domain,...]minSeverity[-maxSeverity] ... file FILENAME

Log [domain,...]minSeverity[-maxSeverity] ... stderr|stdout|syslog
As above, but select messages by range of log severity and by a set of "logging domains". Each
logging domain corresponds to an area of functionality inside Tor. You can specify any number of
severity ranges for a single log statement, each of them prefixed by a comma-separated list of
logging domains. You can prefix a domain with ~ to indicate negation, and use * to indicate "all
domains". If you specify a severity range without a list of domains, it matches all domains.

This is an advanced feature which is most useful for debugging one or two of Tor’s subsystems at a
time.

The currently recognized domains are: general, crypto, net, config, fs, protocol, mm, http, app,
control, circ, rend, bug, dir, dirserv, or, edge, acct, hist, and handshake. Domain names are
case-insensitive.

For example, "Log [handshake]debug [~net,~mm]info notice stdout" sends to stdout: all handshake
messages of any severity, all info-and-higher messages from domains other than networking and memory
management, and all messages of severity notice or higher.

LogMessageDomains 0|1
If 1, Tor includes message domains with each log message. Every log message currently has at least
one domain; most currently have exactly one. This doesn’t affect controller log messages. (Default:
0)

MaxUnparseableDescSizeToLog N bytes|KBytes|MBytes|GBytes|TBytes
Unparseable descriptors (e.g. for votes, consensuses, routers) are logged in separate files by hash,
up to the specified size in total. Note that only files logged during the lifetime of this Tor
process count toward the total; this is intended to be used to debug problems without opening live
servers to resource exhaustion attacks. (Default: 10 MB)

OutboundBindAddress IP
Make all outbound connections originate from the IP address specified. This is only useful when you
have multiple network interfaces, and you want all of Tor’s outgoing connections to use a single one.
This option may be used twice, once with an IPv4 address and once with an IPv6 address. IPv6
addresses should be wrapped in square brackets. This setting will be ignored for connections to the
loopback addresses (127.0.0.0/8 and ::1).

OutboundBindAddressOR IP
Make all outbound non-exit (relay and other) connections originate from the IP address specified.
This option overrides OutboundBindAddress for the same IP version. This option may be used twice,
once with an IPv4 address and once with an IPv6 address. IPv6 addresses should be wrapped in square
brackets. This setting will be ignored for connections to the loopback addresses (127.0.0.0/8 and
::1).

OutboundBindAddressExit IP
Make all outbound exit connections originate from the IP address specified. This option overrides
OutboundBindAddress for the same IP version. This option may be used twice, once with an IPv4 address
and once with an IPv6 address. IPv6 addresses should be wrapped in square brackets. This setting will
be ignored for connections to the loopback addresses (127.0.0.0/8 and ::1).

PidFile FILE
On startup, write our PID to FILE. On clean shutdown, remove FILE. Can not be changed while tor is
running.

ProtocolWarnings 0|1
If 1, Tor will log with severity 'warn' various cases of other parties not following the Tor
specification. Otherwise, they are logged with severity 'info'. (Default: 0)

RunAsDaemon 0|1
If 1, Tor forks and daemonizes to the background. This option has no effect on Windows; instead you
should use the --service command-line option. Can not be changed while tor is running. (Default: 0)

LogTimeGranularity NUM
Set the resolution of timestamps in Tor’s logs to NUM milliseconds. NUM must be positive and either a
divisor or a multiple of 1 second. Note that this option only controls the granularity written by Tor
to a file or console log. Tor does not (for example) "batch up" log messages to affect times logged
by a controller, times attached to syslog messages, or the mtime fields on log files. (Default: 1
second)

TruncateLogFile 0|1
If 1, Tor will overwrite logs at startup and in response to a HUP signal, instead of appending to
them. (Default: 0)

SyslogIdentityTag tag
When logging to syslog, adds a tag to the syslog identity such that log entries are marked with
"Tor-tag". Can not be changed while tor is running. (Default: none)

SafeLogging 0|1|relay
Tor can scrub potentially sensitive strings from log messages (e.g. addresses) by replacing them with
the string [scrubbed]. This way logs can still be useful, but they don’t leave behind personally
identifying information about what sites a user might have visited.

If this option is set to 0, Tor will not perform any scrubbing, if it is set to 1, all potentially
sensitive strings are replaced. If it is set to relay, all log messages generated when acting as a
relay are sanitized, but all messages generated when acting as a client are not. (Default: 1)

User Username
On startup, setuid to this user and setgid to their primary group. Can not be changed while tor is
running.

KeepBindCapabilities 0|1|auto
On Linux, when we are started as root and we switch our identity using the User option, the
KeepBindCapabilities option tells us whether to try to retain our ability to bind to low ports. If
this value is 1, we try to keep the capability; if it is 0 we do not; and if it is auto, we keep the
capability only if we are configured to listen on a low port. Can not be changed while tor is
running. (Default: auto.)

HardwareAccel 0|1
If non-zero, try to use built-in (static) crypto hardware acceleration when available. Can not be
changed while tor is running. (Default: 0)

AccelName NAME
When using OpenSSL hardware crypto acceleration attempt to load the dynamic engine of this name. This
must be used for any dynamic hardware engine. Names can be verified with the openssl engine command.
Can not be changed while tor is running.

AccelDir DIR
Specify this option if using dynamic hardware acceleration and the engine implementation library
resides somewhere other than the OpenSSL default. Can not be changed while tor is running.

AvoidDiskWrites 0|1
If non-zero, try to write to disk less frequently than we would otherwise. This is useful when
running on flash memory or other media that support only a limited number of writes. (Default: 0)

CircuitPriorityHalflife NUM1
If this value is set, we override the default algorithm for choosing which circuit’s cell to deliver
or relay next. When the value is 0, we round-robin between the active circuits on a connection,
delivering one cell from each in turn. When the value is positive, we prefer delivering cells from
whichever connection has the lowest weighted cell count, where cells are weighted exponentially
according to the supplied CircuitPriorityHalflife value (in seconds). If this option is not set at
all, we use the behavior recommended in the current consensus networkstatus. This is an advanced
option; you generally shouldn’t have to mess with it. (Default: not set)

CountPrivateBandwidth 0|1
If this option is set, then Tor’s rate-limiting applies not only to remote connections, but also to
connections to private addresses like 127.0.0.1 or 10.0.0.1. This is mostly useful for debugging
rate-limiting. (Default: 0)

ExtendByEd25519ID 0|1|auto
If this option is set to 1, we always try to include a relay’s Ed25519 ID when telling the proceeding
relay in a circuit to extend to it. If this option is set to 0, we never include Ed25519 IDs when
extending circuits. If the option is set to "default", we obey a parameter in the consensus document.
(Default: auto)

NoExec 0|1
If this option is set to 1, then Tor will never launch another executable, regardless of the settings
of PortForwardingHelper, ClientTransportPlugin, or ServerTransportPlugin. Once this option has been
set to 1, it cannot be set back to 0 without restarting Tor. (Default: 0)

Schedulers KIST|KISTLite|Vanilla
Specify the scheduler type that tor should use. The scheduler is responsible for moving data around
within a Tor process. This is an ordered list by priority which means that the first value will be
tried first and if unavailable, the second one is tried and so on. It is possible to change these
values at runtime. This option mostly effects relays, and most operators should leave it set to its
default value. (Default: KIST,KISTLite,Vanilla)

The possible scheduler types are:

KIST: Kernel-Informed Socket Transport. Tor will use TCP information from the kernel to make informed
decisions regarding how much data to send and when to send it. KIST also handles traffic in batches
(see KISTSchedRunInterval) in order to improve traffic prioritization decisions. As implemented, KIST
will only work on Linux kernel version 2.6.39 or higher.

KISTLite: Same as KIST but without kernel support. Tor will use all the same mechanics as with KIST,
including the batching, but its decisions regarding how much data to send will not be as good.
KISTLite will work on all kernels and operating systems, and the majority of the benefits of KIST are
still realized with KISTLite.

Vanilla: The scheduler that Tor used before KIST was implemented. It sends as much data as possible,
as soon as possible. Vanilla will work on all kernels and operating systems.

KISTSchedRunInterval NUM msec
If KIST or KISTLite is used in the Schedulers option, this controls at which interval the scheduler
tick is. If the value is 0 msec, the value is taken from the consensus if possible else it will
fallback to the default 10 msec. Maximum possible value is 100 msec. (Default: 0 msec)

KISTSockBufSizeFactor NUM
If KIST is used in Schedulers, this is a multiplier of the per-socket limit calculation of the KIST
algorithm. (Default: 1.0)

CLIENT OPTIONS

The following options are useful only for clients (that is, if SocksPort, HTTPTunnelPort, TransPort,
DNSPort, or NATDPort is non-zero):

Bridge [transport] IP:ORPort [fingerprint]
When set along with UseBridges, instructs Tor to use the relay at "IP:ORPort" as a "bridge" relaying
into the Tor network. If "fingerprint" is provided (using the same format as for DirAuthority), we
will verify that the relay running at that location has the right fingerprint. We also use
fingerprint to look up the bridge descriptor at the bridge authority, if it’s provided and if
UpdateBridgesFromAuthority is set too.

If "transport" is provided, it must match a ClientTransportPlugin line. We then use that pluggable
transport’s proxy to transfer data to the bridge, rather than connecting to the bridge directly. Some
transports use a transport-specific method to work out the remote address to connect to. These
transports typically ignore the "IP:ORPort" specified in the bridge line.

Tor passes any "key=val" settings to the pluggable transport proxy as per-connection arguments when
connecting to the bridge. Consult the documentation of the pluggable transport for details of what
arguments it supports.

LearnCircuitBuildTimeout 0|1
If 0, CircuitBuildTimeout adaptive learning is disabled. (Default: 1)

CircuitBuildTimeout NUM
Try for at most NUM seconds when building circuits. If the circuit isn’t open in that time, give up
on it. If LearnCircuitBuildTimeout is 1, this value serves as the initial value to use before a
timeout is learned. If LearnCircuitBuildTimeout is 0, this value is the only value used. (Default: 60
seconds)

CircuitsAvailableTimeout NUM
Tor will attempt to keep at least one open, unused circuit available for this amount of time. This
option governs how long idle circuits are kept open, as well as the amount of time Tor will keep a
circuit open to each of the recently used ports. This way when the Tor client is entirely idle, it
can expire all of its circuits, and then expire its TLS connections. Note that the actual timeout
value is uniformly randomized from the specified value to twice that amount. (Default: 30 minutes;
Max: 24 hours)

CircuitStreamTimeout NUM
If non-zero, this option overrides our internal timeout schedule for how many seconds until we detach
a stream from a circuit and try a new circuit. If your network is particularly slow, you might want
to set this to a number like 60. (Default: 0)

ClientOnly 0|1
If set to 1, Tor will not run as a relay or serve directory requests, even if the ORPort, ExtORPort,
or DirPort options are set. (This config option is mostly unnecessary: we added it back when we were
considering having Tor clients auto-promote themselves to being relays if they were stable and fast
enough. The current behavior is simply that Tor is a client unless ORPort, ExtORPort, or DirPort are
configured.) (Default: 0)

ConnectionPadding 0|1|auto
This option governs Tor’s use of padding to defend against some forms of traffic analysis. If it is
set to auto, Tor will send padding only if both the client and the relay support it. If it is set to
0, Tor will not send any padding cells. If it is set to 1, Tor will still send padding for client
connections regardless of relay support. Only clients may set this option. This option should be
offered via the UI to mobile users for use where bandwidth may be expensive. (Default: auto)

ReducedConnectionPadding 0|1
If set to 1, Tor will not not hold OR connections open for very long, and will send less padding on
these connections. Only clients may set this option. This option should be offered via the UI to
mobile users for use where bandwidth may be expensive. (Default: 0)

ExcludeNodes node,node,...
A list of identity fingerprints, country codes, and address patterns of nodes to avoid when building
a circuit. Country codes are 2-letter ISO3166 codes, and must be wrapped in braces; fingerprints may
be preceded by a dollar sign. (Example: ExcludeNodes ABCD1234CDEF5678ABCD1234CDEF5678ABCD1234, {cc},
255.254.0.0/8)

By default, this option is treated as a preference that Tor is allowed to override in order to keep
working. For example, if you try to connect to a hidden service, but you have excluded all of the
hidden service’s introduction points, Tor will connect to one of them anyway. If you do not want this
behavior, set the StrictNodes option (documented below).

Note also that if you are a relay, this (and the other node selection options below) only affects
your own circuits that Tor builds for you. Clients can still build circuits through you to any node.
Controllers can tell Tor to build circuits through any node.

Country codes are case-insensitive. The code "{??}" refers to nodes whose country can’t be
identified. No country code, including {??}, works if no GeoIPFile can be loaded. See also the
GeoIPExcludeUnknown option below.

ExcludeExitNodes node,node,...
A list of identity fingerprints, country codes, and address patterns of nodes to never use when
picking an exit node---that is, a node that delivers traffic for you outside the Tor network. Note
that any node listed in ExcludeNodes is automatically considered to be part of this list too. See the
ExcludeNodes option for more information on how to specify nodes. See also the caveats on the
"ExitNodes" option below.

GeoIPExcludeUnknown 0|1|auto
If this option is set to auto, then whenever any country code is set in ExcludeNodes or
ExcludeExitNodes, all nodes with unknown country ({??} and possibly {A1}) are treated as excluded as
well. If this option is set to 1, then all unknown countries are treated as excluded in ExcludeNodes
and ExcludeExitNodes. This option has no effect when a GeoIP file isn’t configured or can’t be found.
(Default: auto)

ExitNodes node,node,...
A list of identity fingerprints, country codes, and address patterns of nodes to use as exit
node---that is, a node that delivers traffic for you outside the Tor network. See the ExcludeNodes
option for more information on how to specify nodes.

Note that if you list too few nodes here, or if you exclude too many exit nodes with
ExcludeExitNodes, you can degrade functionality. For example, if none of the exits you list allows
traffic on port 80 or 443, you won’t be able to browse the web.

Note also that not every circuit is used to deliver traffic outside of the Tor network. It is normal
to see non-exit circuits (such as those used to connect to hidden services, those that do directory
fetches, those used for relay reachability self-tests, and so on) that end at a non-exit node. To
keep a node from being used entirely, see ExcludeNodes and StrictNodes.

The ExcludeNodes option overrides this option: any node listed in both ExitNodes and ExcludeNodes is
treated as excluded.

The .exit address notation, if enabled via MapAddress, overrides this option.

EntryNodes node,node,...
A list of identity fingerprints and country codes of nodes to use for the first hop in your normal
circuits. Normal circuits include all circuits except for direct connections to directory servers.
The Bridge option overrides this option; if you have configured bridges and UseBridges is 1, the
Bridges are used as your entry nodes.

The ExcludeNodes option overrides this option: any node listed in both EntryNodes and ExcludeNodes is
treated as excluded. See the ExcludeNodes option for more information on how to specify nodes.

StrictNodes 0|1
If StrictNodes is set to 1, Tor will treat solely the ExcludeNodes option as a requirement to follow
for all the circuits you generate, even if doing so will break functionality for you (StrictNodes
applies to neither ExcludeExitNodes nor to ExitNodes). If StrictNodes is set to 0, Tor will still try
to avoid nodes in the ExcludeNodes list, but it will err on the side of avoiding unexpected errors.
Specifically, StrictNodes 0 tells Tor that it is okay to use an excluded node when it is necessary to
perform relay reachability self-tests, connect to a hidden service, provide a hidden service to a
client, fulfill a .exit request, upload directory information, or download directory information.
(Default: 0)

FascistFirewall 0|1
If 1, Tor will only create outgoing connections to ORs running on ports that your firewall allows
(defaults to 80 and 443; see FirewallPorts). This will allow you to run Tor as a client behind a
firewall with restrictive policies, but will not allow you to run as a server behind such a firewall.
If you prefer more fine-grained control, use ReachableAddresses instead.

FirewallPorts PORTS
A list of ports that your firewall allows you to connect to. Only used when FascistFirewall is set.
This option is deprecated; use ReachableAddresses instead. (Default: 80, 443)

ReachableAddresses IP[/MASK][:PORT]...
A comma-separated list of IP addresses and ports that your firewall allows you to connect to. The
format is as for the addresses in ExitPolicy, except that "accept" is understood unless "reject" is
explicitly provided. For example, 'ReachableAddresses 99.0.0.0/8, reject 18.0.0.0/8:80, accept *:80'
means that your firewall allows connections to everything inside net 99, rejects port 80 connections
to net 18, and accepts connections to port 80 otherwise. (Default: 'accept *:*'.)

ReachableDirAddresses IP[/MASK][:PORT]...
Like ReachableAddresses, a list of addresses and ports. Tor will obey these restrictions when
fetching directory information, using standard HTTP GET requests. If not set explicitly then the
value of ReachableAddresses is used. If HTTPProxy is set then these connections will go through that
proxy. (DEPRECATED: This option has had no effect for some time.)

ReachableORAddresses IP[/MASK][:PORT]...
Like ReachableAddresses, a list of addresses and ports. Tor will obey these restrictions when
connecting to Onion Routers, using TLS/SSL. If not set explicitly then the value of
ReachableAddresses is used. If HTTPSProxy is set then these connections will go through that proxy.

The separation between ReachableORAddresses and ReachableDirAddresses is only interesting when you
are connecting through proxies (see HTTPProxy and HTTPSProxy). Most proxies limit TLS connections
(which Tor uses to connect to Onion Routers) to port 443, and some limit HTTP GET requests (which Tor
uses for fetching directory information) to port 80.

HidServAuth onion-address auth-cookie [service-name]
Client authorization for a hidden service. Valid onion addresses contain 16 characters in a-z2-7 plus
".onion", and valid auth cookies contain 22 characters in A-Za-z0-9+/. The service name is only used
for internal purposes, e.g., for Tor controllers. This option may be used multiple times for
different hidden services. If a hidden service uses authorization and this option is not set, the
hidden service is not accessible. Hidden services can be configured to require authorization using
the HiddenServiceAuthorizeClient option.

LongLivedPorts PORTS
A list of ports for services that tend to have long-running connections (e.g. chat and interactive
shells). Circuits for streams that use these ports will contain only high-uptime nodes, to reduce the
chance that a node will go down before the stream is finished. Note that the list is also honored for
circuits (both client and service side) involving hidden services whose virtual port is in this list.
(Default: 21, 22, 706, 1863, 5050, 5190, 5222, 5223, 6523, 6667, 6697, 8300)

MapAddress address newaddress
When a request for address arrives to Tor, it will transform to newaddress before processing it. For
example, if you always want connections to www.example.com to exit via torserver (where torserver is
the fingerprint of the server), use "MapAddress www.example.com www.example.com.torserver.exit". If
the value is prefixed with a "*.", matches an entire domain. For example, if you always want
connections to example.com and any if its subdomains to exit via torserver (where torserver is the
fingerprint of the server), use "MapAddress *.example.com *.example.com.torserver.exit". (Note the
leading "*." in each part of the directive.) You can also redirect all subdomains of a domain to a
single address. For example, "MapAddress *.example.com www.example.com".

NOTES:

1. When evaluating MapAddress expressions Tor stops when it hits the most recently added expression
that matches the requested address. So if you have the following in your torrc,
www.torproject.org will map to 1.1.1.1:

MapAddress www.torproject.org 2.2.2.2
MapAddress www.torproject.org 1.1.1.1

2. Tor evaluates the MapAddress configuration until it finds no matches. So if you have the
following in your torrc, www.torproject.org will map to 2.2.2.2:

MapAddress 1.1.1.1 2.2.2.2
MapAddress www.torproject.org 1.1.1.1

3. The following MapAddress expression is invalid (and will be ignored) because you cannot map from
a specific address to a wildcard address:

MapAddress www.torproject.org *.torproject.org.torserver.exit

4. Using a wildcard to match only part of a string (as in *ample.com) is also invalid.

NewCircuitPeriod NUM
Every NUM seconds consider whether to build a new circuit. (Default: 30 seconds)

MaxCircuitDirtiness NUM
Feel free to reuse a circuit that was first used at most NUM seconds ago, but never attach a new
stream to a circuit that is too old. For hidden services, this applies to the last time a circuit was
used, not the first. Circuits with streams constructed with SOCKS authentication via SocksPorts that
have KeepAliveIsolateSOCKSAuth also remain alive for MaxCircuitDirtiness seconds after carrying the
last such stream. (Default: 10 minutes)

MaxClientCircuitsPending NUM
Do not allow more than NUM circuits to be pending at a time for handling client streams. A circuit is
pending if we have begun constructing it, but it has not yet been completely constructed. (Default:
32)

NodeFamily node,node,...
The Tor servers, defined by their identity fingerprints, constitute a "family" of similar or
co-administered servers, so never use any two of them in the same circuit. Defining a NodeFamily is
only needed when a server doesn’t list the family itself (with MyFamily). This option can be used
multiple times; each instance defines a separate family. In addition to nodes, you can also list IP
address and ranges and country codes in {curly braces}. See the ExcludeNodes option for more
information on how to specify nodes.

EnforceDistinctSubnets 0|1
If 1, Tor will not put two servers whose IP addresses are "too close" on the same circuit. Currently,
two addresses are "too close" if they lie in the same /16 range. (Default: 1)

SocksPort [address:]port|unix:path|auto [flags] [isolation flags]
Open this port to listen for connections from SOCKS-speaking applications. Set this to 0 if you don’t
want to allow application connections via SOCKS. Set it to "auto" to have Tor pick a port for you.
This directive can be specified multiple times to bind to multiple addresses/ports. If a unix domain
socket is used, you may quote the path using standard C escape sequences. (Default: 9050)

NOTE: Although this option allows you to specify an IP address other than localhost, you should do so
only with extreme caution. The SOCKS protocol is unencrypted and (as we use it) unauthenticated, so
exposing it in this way could leak your information to anybody watching your network, and allow
anybody to use your computer as an open proxy.

The isolation flags arguments give Tor rules for which streams received on this SocksPort are allowed
to share circuits with one another. Recognized isolation flags are:

IsolateClientAddr
Don’t share circuits with streams from a different client address. (On by default and strongly
recommended when supported; you can disable it with NoIsolateClientAddr. Unsupported and
force-disabled when using Unix domain sockets.)

IsolateSOCKSAuth
Don’t share circuits with streams for which different SOCKS authentication was provided. (For
HTTPTunnelPort connections, this option looks at the Proxy-Authorization and
X-Tor-Stream-Isolation headers. On by default; you can disable it with NoIsolateSOCKSAuth.)

IsolateClientProtocol
Don’t share circuits with streams using a different protocol. (SOCKS 4, SOCKS 5, TransPort
connections, NATDPort connections, and DNSPort requests are all considered to be different
protocols.)

IsolateDestPort
Don’t share circuits with streams targeting a different destination port.

IsolateDestAddr
Don’t share circuits with streams targeting a different destination address.

KeepAliveIsolateSOCKSAuth
If IsolateSOCKSAuth is enabled, keep alive circuits while they have at least one stream with
SOCKS authentication active. After such a circuit is idle for more than MaxCircuitDirtiness
seconds, it can be closed.

SessionGroup=INT
If no other isolation rules would prevent it, allow streams on this port to share circuits with
streams from every other port with the same session group. (By default, streams received on
different SocksPorts, TransPorts, etc are always isolated from one another. This option overrides
that behavior.)

Other recognized flags for a SocksPort are:

NoIPv4Traffic
Tell exits to not connect to IPv4 addresses in response to SOCKS requests on this connection.

IPv6Traffic
Tell exits to allow IPv6 addresses in response to SOCKS requests on this connection, so long as
SOCKS5 is in use. (SOCKS4 can’t handle IPv6.)

PreferIPv6
Tells exits that, if a host has both an IPv4 and an IPv6 address, we would prefer to connect to
it via IPv6. (IPv4 is the default.)

NoDNSRequest
Do not ask exits to resolve DNS addresses in SOCKS5 requests. Tor will connect to IPv4 addresses,
IPv6 addresses (if IPv6Traffic is set) and .onion addresses.

NoOnionTraffic
Do not connect to .onion addresses in SOCKS5 requests.

OnionTrafficOnly
Tell the tor client to only connect to .onion addresses in response to SOCKS5 requests on this
connection. This is equivalent to NoDNSRequest, NoIPv4Traffic, NoIPv6Traffic. The corresponding
NoOnionTrafficOnly flag is not supported.

CacheIPv4DNS
Tells the client to remember IPv4 DNS answers we receive from exit nodes via this connection. (On
by default.)

CacheIPv6DNS
Tells the client to remember IPv6 DNS answers we receive from exit nodes via this connection.

GroupWritable
Unix domain sockets only: makes the socket get created as group-writable.

WorldWritable
Unix domain sockets only: makes the socket get created as world-writable.

CacheDNS
Tells the client to remember all DNS answers we receive from exit nodes via this connection.

UseIPv4Cache
Tells the client to use any cached IPv4 DNS answers we have when making requests via this
connection. (NOTE: This option, along UseIPv6Cache and UseDNSCache, can harm your anonymity, and
probably won’t help performance as much as you might expect. Use with care!)

UseIPv6Cache
Tells the client to use any cached IPv6 DNS answers we have when making requests via this
connection.

UseDNSCache
Tells the client to use any cached DNS answers we have when making requests via this connection.

PreferIPv6Automap
When serving a hostname lookup request on this port that should get automapped (according to
AutomapHostsOnResolve), if we could return either an IPv4 or an IPv6 answer, prefer an IPv6
answer. (On by default.)

PreferSOCKSNoAuth
Ordinarily, when an application offers both "username/password authentication" and "no
authentication" to Tor via SOCKS5, Tor selects username/password authentication so that
IsolateSOCKSAuth can work. This can confuse some applications, if they offer a username/password
combination then get confused when asked for one. You can disable this behavior, so that Tor will
select "No authentication" when IsolateSOCKSAuth is disabled, or when this option is set.

Flags are processed left to right. If flags conflict, the last flag on the line is used, and all
earlier flags are ignored. No error is issued for conflicting flags.

SocksPolicy policy,policy,...
Set an entrance policy for this server, to limit who can connect to the SocksPort and DNSPort ports.
The policies have the same form as exit policies below, except that port specifiers are ignored. Any
address not matched by some entry in the policy is accepted.

SocksTimeout NUM
Let a socks connection wait NUM seconds handshaking, and NUM seconds unattached waiting for an
appropriate circuit, before we fail it. (Default: 2 minutes)

TokenBucketRefillInterval NUM [msec|second]
Set the refill interval of Tor’s token bucket to NUM milliseconds. NUM must be between 1 and 1000,
inclusive. Note that the configured bandwidth limits are still expressed in bytes per second: this
option only affects the frequency with which Tor checks to see whether previously exhausted
connections may read again. Can not be changed while tor is running. (Default: 100 msec)

TrackHostExits host,.domain,...
For each value in the comma separated list, Tor will track recent connections to hosts that match
this value and attempt to reuse the same exit node for each. If the value is prepended with a '.', it
is treated as matching an entire domain. If one of the values is just a '.', it means match
everything. This option is useful if you frequently connect to sites that will expire all your
authentication cookies (i.e. log you out) if your IP address changes. Note that this option does have
the disadvantage of making it more clear that a given history is associated with a single user.
However, most people who would wish to observe this will observe it through cookies or other
protocol-specific means anyhow.

TrackHostExitsExpire NUM
Since exit servers go up and down, it is desirable to expire the association between host and exit
server after NUM seconds. The default is 1800 seconds (30 minutes).

UpdateBridgesFromAuthority 0|1
When set (along with UseBridges), Tor will try to fetch bridge descriptors from the configured bridge
authorities when feasible. It will fall back to a direct request if the authority responds with a
404. (Default: 0)

UseBridges 0|1
When set, Tor will fetch descriptors for each bridge listed in the "Bridge" config lines, and use
these relays as both entry guards and directory guards. (Default: 0)

UseEntryGuards 0|1
If this option is set to 1, we pick a few long-term entry servers, and try to stick with them. This
is desirable because constantly changing servers increases the odds that an adversary who owns some
servers will observe a fraction of your paths. Entry Guards can not be used by Directory Authorities,
Single Onion Services, and Tor2web clients. In these cases, the this option is ignored. (Default: 1)

GuardfractionFile FILENAME
V3 authoritative directories only. Configures the location of the guardfraction file which contains
information about how long relays have been guards. (Default: unset)

UseGuardFraction 0|1|auto
This torrc option specifies whether clients should use the guardfraction information found in the
consensus during path selection. If it’s set to auto, clients will do what the UseGuardFraction
consensus parameter tells them to do. (Default: auto)

NumEntryGuards NUM
If UseEntryGuards is set to 1, we will try to pick a total of NUM routers as long-term entries for
our circuits. If NUM is 0, we try to learn the number from the guard-n-primary-guards-to-use
consensus parameter, and default to 1 if the consensus parameter isn’t set. (Default: 0)

NumDirectoryGuards NUM
If UseEntryGuards is set to 1, we try to make sure we have at least NUM routers to use as directory
guards. If this option is set to 0, use the value from the guard-n-primary-dir-guards-to-use
consensus parameter, and default to 3 if the consensus parameter isn’t set. (Default: 0)

GuardLifetime N days|weeks|months
If nonzero, and UseEntryGuards is set, minimum time to keep a guard before picking a new one. If
zero, we use the GuardLifetime parameter from the consensus directory. No value here may be less than
1 month or greater than 5 years; out-of-range values are clamped. (Default: 0)

SafeSocks 0|1
When this option is enabled, Tor will reject application connections that use unsafe variants of the
socks protocol — ones that only provide an IP address, meaning the application is doing a DNS resolve
first. Specifically, these are socks4 and socks5 when not doing remote DNS. (Default: 0)

TestSocks 0|1
When this option is enabled, Tor will make a notice-level log entry for each connection to the Socks
port indicating whether the request used a safe socks protocol or an unsafe one (see above entry on
SafeSocks). This helps to determine whether an application using Tor is possibly leaking DNS
requests. (Default: 0)

VirtualAddrNetworkIPv4 IPv4Address/bits

VirtualAddrNetworkIPv6 [IPv6Address]/bits
When Tor needs to assign a virtual (unused) address because of a MAPADDRESS command from the
controller or the AutomapHostsOnResolve feature, Tor picks an unassigned address from this range.
(Defaults: 127.192.0.0/10 and [FE80::]/10 respectively.)

When providing proxy server service to a network of computers using a tool like dns-proxy-tor, change
the IPv4 network to "10.192.0.0/10" or "172.16.0.0/12" and change the IPv6 network to "[FC00::]/7".
The default VirtualAddrNetwork address ranges on a properly configured machine will route to the
loopback or link-local interface. The maximum number of bits for the network prefix is set to 104 for
IPv6 and 16 for IPv4. However, a wider network - smaller prefix length

• is preferable since it reduces the chances for an attacker to guess the used IP. For local use,
no change to the default VirtualAddrNetwork setting is needed.

AllowNonRFC953Hostnames 0|1
When this option is disabled, Tor blocks hostnames containing illegal characters (like @ and :)
rather than sending them to an exit node to be resolved. This helps trap accidental attempts to
resolve URLs and so on. (Default: 0)

HTTPTunnelPort [address:]port|auto [isolation flags]
Open this port to listen for proxy connections using the "HTTP CONNECT" protocol instead of SOCKS.
Set this to 0 0 if you don’t want to allow "HTTP CONNECT" connections. Set the port to "auto" to have
Tor pick a port for you. This directive can be specified multiple times to bind to multiple
addresses/ports. See SOCKSPort for an explanation of isolation flags. (Default: 0)

TransPort [address:]port|auto [isolation flags]
Open this port to listen for transparent proxy connections. Set this to 0 if you don’t want to allow
transparent proxy connections. Set the port to "auto" to have Tor pick a port for you. This directive
can be specified multiple times to bind to multiple addresses/ports. See SOCKSPort for an explanation
of isolation flags.

TransPort requires OS support for transparent proxies, such as BSDs' pf or Linux’s IPTables. If
you’re planning to use Tor as a transparent proxy for a network, you’ll want to examine and change
VirtualAddrNetwork from the default setting. (Default: 0)

TransProxyType default|TPROXY|ipfw|pf-divert
TransProxyType may only be enabled when there is transparent proxy listener enabled.

Set this to "TPROXY" if you wish to be able to use the TPROXY Linux module to transparently proxy
connections that are configured using the TransPort option. Detailed information on how to configure
the TPROXY feature can be found in the Linux kernel source tree in the file
Documentation/networking/tproxy.txt.

Set this option to "ipfw" to use the FreeBSD ipfw interface.

On *BSD operating systems when using pf, set this to "pf-divert" to take advantage of divert-to
rules, which do not modify the packets like rdr-to rules do. Detailed information on how to configure
pf to use divert-to rules can be found in the pf.conf(5) manual page. On OpenBSD, divert-to is
available to use on versions greater than or equal to OpenBSD 4.4.

Set this to "default", or leave it unconfigured, to use regular IPTables on Linux, or to use pf
rdr-to rules on *BSD systems.

(Default: "default".)

NATDPort [address:]port|auto [isolation flags]
Open this port to listen for connections from old versions of ipfw (as included in old versions of
FreeBSD, etc) using the NATD protocol. Use 0 if you don’t want to allow NATD connections. Set the
port to "auto" to have Tor pick a port for you. This directive can be specified multiple times to
bind to multiple addresses/ports. See SocksPort for an explanation of isolation flags.

This option is only for people who cannot use TransPort. (Default: 0)

AutomapHostsOnResolve 0|1
When this option is enabled, and we get a request to resolve an address that ends with one of the
suffixes in AutomapHostsSuffixes, we map an unused virtual address to that address, and return the
new virtual address. This is handy for making ".onion" addresses work with applications that resolve
an address and then connect to it. (Default: 0)

AutomapHostsSuffixes SUFFIX,SUFFIX,...
A comma-separated list of suffixes to use with AutomapHostsOnResolve. The "." suffix is equivalent to
"all addresses." (Default: .exit,.onion).

DNSPort [address:]port|auto [isolation flags]
If non-zero, open this port to listen for UDP DNS requests, and resolve them anonymously. This port
only handles A, AAAA, and PTR requests---it doesn’t handle arbitrary DNS request types. Set the port
to "auto" to have Tor pick a port for you. This directive can be specified multiple times to bind to
multiple addresses/ports. See SocksPort for an explanation of isolation flags. (Default: 0)

ClientDNSRejectInternalAddresses 0|1
If true, Tor does not believe any anonymously retrieved DNS answer that tells it that an address
resolves to an internal address (like 127.0.0.1 or 192.168.0.1). This option prevents certain
browser-based attacks; it is not allowed to be set on the default network. (Default: 1)

ClientRejectInternalAddresses 0|1
If true, Tor does not try to fulfill requests to connect to an internal address (like 127.0.0.1 or
192.168.0.1) unless an exit node is specifically requested (for example, via a .exit hostname, or a
controller request). If true, multicast DNS hostnames for machines on the local network (of the form
*.local) are also rejected. (Default: 1)

DownloadExtraInfo 0|1
If true, Tor downloads and caches "extra-info" documents. These documents contain information about
servers other than the information in their regular server descriptors. Tor does not use this
information for anything itself; to save bandwidth, leave this option turned off. (Default: 0)

WarnPlaintextPorts port,port,...
Tells Tor to issue a warnings whenever the user tries to make an anonymous connection to one of these
ports. This option is designed to alert users to services that risk sending passwords in the clear.
(Default: 23,109,110,143)

RejectPlaintextPorts port,port,...
Like WarnPlaintextPorts, but instead of warning about risky port uses, Tor will instead refuse to
make the connection. (Default: None)

OptimisticData 0|1|auto
When this option is set, and Tor is using an exit node that supports the feature, it will try
optimistically to send data to the exit node without waiting for the exit node to report whether the
connection succeeded. This can save a round-trip time for protocols like HTTP where the client talks
first. If OptimisticData is set to auto, Tor will look at the UseOptimisticData parameter in the
networkstatus. (Default: auto)

Tor2webMode 0|1
When this option is set, Tor connects to hidden services non-anonymously. This option also disables
client connections to non-hidden-service hostnames through Tor. It must only be used when running a
tor2web Hidden Service web proxy. To enable this option the compile time flag --enable-tor2web-mode
must be specified. Since Tor2webMode is non-anonymous, you can not run an anonymous Hidden Service on
a tor version compiled with Tor2webMode. (Default: 0)

Tor2webRendezvousPoints node,node,...
A list of identity fingerprints, nicknames, country codes and address patterns of nodes that are
allowed to be used as RPs in HS circuits; any other nodes will not be used as RPs. (Example:
Tor2webRendezvousPoints Fastyfasty, ABCD1234CDEF5678ABCD1234CDEF5678ABCD1234, {cc}, 255.254.0.0/8)

This feature can only be used if Tor2webMode is also enabled.

ExcludeNodes have higher priority than Tor2webRendezvousPoints, which means that nodes specified in
ExcludeNodes will not be picked as RPs.

If no nodes in Tor2webRendezvousPoints are currently available for use, Tor will choose a random node
when building HS circuits.

UseMicrodescriptors 0|1|auto
Microdescriptors are a smaller version of the information that Tor needs in order to build its
circuits. Using microdescriptors makes Tor clients download less directory information, thus saving
bandwidth. Directory caches need to fetch regular descriptors and microdescriptors, so this option
doesn’t save any bandwidth for them. If this option is set to "auto" (recommended) then it is on for
all clients that do not set FetchUselessDescriptors. (Default: auto)

PathBiasCircThreshold NUM

PathBiasNoticeRate NUM

PathBiasWarnRate NUM

PathBiasExtremeRate NUM

PathBiasDropGuards NUM

PathBiasScaleThreshold NUM
These options override the default behavior of Tor’s (currently experimental) path bias detection
algorithm. To try to find broken or misbehaving guard nodes, Tor looks for nodes where more than a
certain fraction of circuits through that guard fail to get built.

The PathBiasCircThreshold option controls how many circuits we need to build through a guard before
we make these checks. The PathBiasNoticeRate, PathBiasWarnRate and PathBiasExtremeRate options
control what fraction of circuits must succeed through a guard so we won’t write log messages. If
less than PathBiasExtremeRate circuits succeed and PathBiasDropGuards is set to 1, we disable use of
that guard.

When we have seen more than PathBiasScaleThreshold circuits through a guard, we scale our
observations by 0.5 (governed by the consensus) so that new observations don’t get swamped by old
ones.

By default, or if a negative value is provided for one of these options, Tor uses reasonable defaults
from the networkstatus consensus document. If no defaults are available there, these options default
to 150, .70, .50, .30, 0, and 300 respectively.

PathBiasUseThreshold NUM

PathBiasNoticeUseRate NUM

PathBiasExtremeUseRate NUM

PathBiasScaleUseThreshold NUM
Similar to the above options, these options override the default behavior of Tor’s (currently
experimental) path use bias detection algorithm.

Where as the path bias parameters govern thresholds for successfully building circuits, these four
path use bias parameters govern thresholds only for circuit usage. Circuits which receive no stream
usage are not counted by this detection algorithm. A used circuit is considered successful if it is
capable of carrying streams or otherwise receiving well-formed responses to RELAY cells.

ClientUseIPv4 0|1
If this option is set to 0, Tor will avoid connecting to directory servers and entry nodes over IPv4.
Note that clients with an IPv4 address in a Bridge, proxy, or pluggable transport line will try
connecting over IPv4 even if ClientUseIPv4 is set to 0. (Default: 1)

ClientUseIPv6 0|1
If this option is set to 1, Tor might connect to directory servers or entry nodes over IPv6. Note
that clients configured with an IPv6 address in a Bridge, proxy, or pluggable transport line will try
connecting over IPv6 even if ClientUseIPv6 is set to 0. (Default: 0)

ClientPreferIPv6DirPort 0|1|auto
If this option is set to 1, Tor prefers a directory port with an IPv6 address over one with IPv4, for
direct connections, if a given directory server has both. (Tor also prefers an IPv6 DirPort if
IPv4Client is set to 0.) If this option is set to auto, clients prefer IPv4. Other things may
influence the choice. This option breaks a tie to the favor of IPv6. (Default: auto) (DEPRECATED:
This option has had no effect for some time.)

ClientPreferIPv6ORPort 0|1|auto
If this option is set to 1, Tor prefers an OR port with an IPv6 address over one with IPv4 if a given
entry node has both. (Tor also prefers an IPv6 ORPort if IPv4Client is set to 0.) If this option is
set to auto, Tor bridge clients prefer the configured bridge address, and other clients prefer IPv4.
Other things may influence the choice. This option breaks a tie to the favor of IPv6. (Default: auto)

PathsNeededToBuildCircuits NUM
Tor clients don’t build circuits for user traffic until they know about enough of the network so that
they could potentially construct enough of the possible paths through the network. If this option is
set to a fraction between 0.25 and 0.95, Tor won’t build circuits until it has enough descriptors or
microdescriptors to construct that fraction of possible paths. Note that setting this option too low
can make your Tor client less anonymous, and setting it too high can prevent your Tor client from
bootstrapping. If this option is negative, Tor will use a default value chosen by the directory
authorities. If the directory authorities do not choose a value, Tor will default to 0.6. (Default:
-1.)

ClientBootstrapConsensusAuthorityDownloadSchedule N,N,...
Schedule for when clients should download consensuses from authorities if they are bootstrapping
(that is, they don’t have a usable, reasonably live consensus). Only used by clients fetching from a
list of fallback directory mirrors. This schedule is advanced by (potentially concurrent) connection
attempts, unlike other schedules, which are advanced by connection failures. (Default: 6, 11, 3600,
10800, 25200, 54000, 111600, 262800)

ClientBootstrapConsensusFallbackDownloadSchedule N,N,...
Schedule for when clients should download consensuses from fallback directory mirrors if they are
bootstrapping (that is, they don’t have a usable, reasonably live consensus). Only used by clients
fetching from a list of fallback directory mirrors. This schedule is advanced by (potentially
concurrent) connection attempts, unlike other schedules, which are advanced by connection failures.
(Default: 0, 1, 4, 11, 3600, 10800, 25200, 54000, 111600, 262800)

ClientBootstrapConsensusAuthorityOnlyDownloadSchedule N,N,...
Schedule for when clients should download consensuses from authorities if they are bootstrapping
(that is, they don’t have a usable, reasonably live consensus). Only used by clients which don’t have
or won’t fetch from a list of fallback directory mirrors. This schedule is advanced by (potentially
concurrent) connection attempts, unlike other schedules, which are advanced by connection failures.
(Default: 0, 3, 7, 3600, 10800, 25200, 54000, 111600, 262800)

ClientBootstrapConsensusMaxDownloadTries NUM
Try this many times to download a consensus while bootstrapping using fallback directory mirrors
before giving up. (Default: 7)

ClientBootstrapConsensusAuthorityOnlyMaxDownloadTries NUM
Try this many times to download a consensus while bootstrapping using authorities before giving up.
(Default: 4)

ClientBootstrapConsensusMaxInProgressTries NUM
Try this many simultaneous connections to download a consensus before waiting for one to complete,
timeout, or error out. (Default: 3)

SERVER OPTIONS

The following options are useful only for servers (that is, if ORPort is non-zero):

Address address
The IPv4 address of this server, or a fully qualified domain name of this server that resolves to an
IPv4 address. You can leave this unset, and Tor will try to guess your IPv4 address. This IPv4
address is the one used to tell clients and other servers where to find your Tor server; it doesn’t
affect the address that your server binds to. To bind to a different address, use the ORPort and
OutboundBindAddress options.

AssumeReachable 0|1
This option is used when bootstrapping a new Tor network. If set to 1, don’t do self-reachability
testing; just upload your server descriptor immediately. If AuthoritativeDirectory is also set, this
option instructs the dirserver to bypass remote reachability testing too and list all connected
servers as running.

BridgeRelay 0|1
Sets the relay to act as a "bridge" with respect to relaying connections from bridge users to the Tor
network. It mainly causes Tor to publish a server descriptor to the bridge database, rather than to
the public directory authorities.

BridgeDistribution string
If set along with BridgeRelay, Tor will include a new line in its bridge descriptor which indicates
to the BridgeDB service how it would like its bridge address to be given out. Set it to "none" if you
want BridgeDB to avoid distributing your bridge address, or "any" to let BridgeDB decide. (Default:
any)

Note: as of Oct 2017, the BridgeDB part of this option is not yet implemented. Until BridgeDB is
updated to obey this option, your bridge will make this request, but it will not (yet) be obeyed.

ContactInfo email_address
Administrative contact information for this relay or bridge. This line can be used to contact you if
your relay or bridge is misconfigured or something else goes wrong. Note that we archive and publish
all descriptors containing these lines and that Google indexes them, so spammers might also collect
them. You may want to obscure the fact that it’s an email address and/or generate a new address for
this purpose.

ContactInfo must be set to a working address if you run more than one relay or bridge. (Really,
everybody running a relay or bridge should set it.)

ExitRelay 0|1|auto
Tells Tor whether to run as an exit relay. If Tor is running as a non-bridge server, and ExitRelay is
set to 1, then Tor allows traffic to exit according to the ExitPolicy option (or the default
ExitPolicy if none is specified).

If ExitRelay is set to 0, no traffic is allowed to exit, and the ExitPolicy option is ignored.

If ExitRelay is set to "auto", then Tor behaves as if it were set to 1, but warns the user if this
would cause traffic to exit. In a future version, the default value will be 0. (Default: auto)

ExitPolicy policy,policy,...
Set an exit policy for this server. Each policy is of the form "accept[6]|reject[6]
ADDR[/MASK][:PORT]". If /MASK is omitted then this policy just applies to the host given. Instead of
giving a host or network you can also use "*" to denote the universe (0.0.0.0/0 and ::/128), or *4 to
denote all IPv4 addresses, and *6 to denote all IPv6 addresses. PORT can be a single port number, an
interval of ports "FROM_PORT-TO_PORT", or "*". If PORT is omitted, that means "*".

For example, "accept 18.7.22.69:*,reject 18.0.0.0/8:*,accept *:*" would reject any IPv4 traffic
destined for MIT except for web.mit.edu, and accept any other IPv4 or IPv6 traffic.

Tor also allows IPv6 exit policy entries. For instance, "reject6 [FC00::]/7:*" rejects all
destinations that share 7 most significant bit prefix with address FC00::. Respectively, "accept6
[C000::]/3:*" accepts all destinations that share 3 most significant bit prefix with address C000::.

accept6 and reject6 only produce IPv6 exit policy entries. Using an IPv4 address with accept6 or
reject6 is ignored and generates a warning. accept/reject allows either IPv4 or IPv6 addresses. Use
*4 as an IPv4 wildcard address, and *6 as an IPv6 wildcard address. accept/reject * expands to
matching IPv4 and IPv6 wildcard address rules.

To specify all IPv4 and IPv6 internal and link-local networks (including 0.0.0.0/8, 169.254.0.0/16,
127.0.0.0/8, 192.168.0.0/16, 10.0.0.0/8, 172.16.0.0/12, [::]/8, [FC00::]/7, [FE80::]/10, [FEC0::]/10,
[FF00::]/8, and [::]/127), you can use the "private" alias instead of an address. ("private" always
produces rules for IPv4 and IPv6 addresses, even when used with accept6/reject6.)

Private addresses are rejected by default (at the beginning of your exit policy), along with any
configured primary public IPv4 and IPv6 addresses. These private addresses are rejected unless you
set the ExitPolicyRejectPrivate config option to 0. For example, once you’ve done that, you could
allow HTTP to 127.0.0.1 and block all other connections to internal networks with "accept
127.0.0.1:80,reject private:*", though that may also allow connections to your own computer that are
addressed to its public (external) IP address. See RFC 1918 and RFC 3330 for more details about
internal and reserved IP address space. See ExitPolicyRejectLocalInterfaces if you want to block
every address on the relay, even those that aren’t advertised in the descriptor.

This directive can be specified multiple times so you don’t have to put it all on one line.

Policies are considered first to last, and the first match wins. If you want to allow the same ports
on IPv4 and IPv6, write your rules using accept/reject *. If you want to allow different ports on
IPv4 and IPv6, write your IPv6 rules using accept6/reject6 *6, and your IPv4 rules using
accept/reject *4. If you want to _replace_ the default exit policy, end your exit policy with either
a reject *:* or an accept *:*. Otherwise, you’re _augmenting_ (prepending to) the default exit
policy. The default exit policy is:

reject *:25
reject *:119
reject *:135-139
reject *:445
reject *:563
reject *:1214
reject *:4661-4666
reject *:6346-6429
reject *:6699
reject *:6881-6999
accept *:*

Since the default exit policy uses accept/reject *, it applies to both IPv4 and IPv6 addresses.

ExitPolicyRejectPrivate 0|1
Reject all private (local) networks, along with the relay’s advertised public IPv4 and IPv6
addresses, at the beginning of your exit policy. See above entry on ExitPolicy. (Default: 1)

ExitPolicyRejectLocalInterfaces 0|1
Reject all IPv4 and IPv6 addresses that the relay knows about, at the beginning of your exit policy.
This includes any OutboundBindAddress, the bind addresses of any port options, such as ControlPort or
DNSPort, and any public IPv4 and IPv6 addresses on any interface on the relay. (If IPv6Exit is not
set, all IPv6 addresses will be rejected anyway.) See above entry on ExitPolicy. This option is off
by default, because it lists all public relay IP addresses in the ExitPolicy, even those relay
operators might prefer not to disclose. (Default: 0)

IPv6Exit 0|1
If set, and we are an exit node, allow clients to use us for IPv6 traffic. (Default: 0)

MaxOnionQueueDelay NUM [msec|second]
If we have more onionskins queued for processing than we can process in this amount of time, reject
new ones. (Default: 1750 msec)

MyFamily fingerprint,fingerprint,...
Declare that this Tor relay is controlled or administered by a group or organization identical or
similar to that of the other relays, defined by their (possibly $-prefixed) identity fingerprints.
This option can be repeated many times, for convenience in defining large families: all fingerprints
in all MyFamily lines are merged into one list. When two relays both declare that they are in the
same 'family', Tor clients will not use them in the same circuit. (Each relay only needs to list the
other servers in its family; it doesn’t need to list itself, but it won’t hurt if it does.) Do not
list any bridge relay as it would compromise its concealment.

When listing a node, it’s better to list it by fingerprint than by nickname: fingerprints are more
reliable.

If you run more than one relay, the MyFamily option on each relay must list all other relays, as
described above.

Nickname name
Set the server’s nickname to 'name'. Nicknames must be between 1 and 19 characters inclusive, and
must contain only the characters [a-zA-Z0-9].

NumCPUs num
How many processes to use at once for decrypting onionskins and other parallelizable operations. If
this is set to 0, Tor will try to detect how many CPUs you have, defaulting to 1 if it can’t tell.
(Default: 0)

ORPort [address:]PORT|auto [flags]
Advertise this port to listen for connections from Tor clients and servers. This option is required
to be a Tor server. Set it to "auto" to have Tor pick a port for you. Set it to 0 to not run an
ORPort at all. This option can occur more than once. (Default: 0)

Tor recognizes these flags on each ORPort:

NoAdvertise
By default, we bind to a port and tell our users about it. If NoAdvertise is specified, we don’t
advertise, but listen anyway. This can be useful if the port everybody will be connecting to (for
example, one that’s opened on our firewall) is somewhere else.

NoListen
By default, we bind to a port and tell our users about it. If NoListen is specified, we don’t
bind, but advertise anyway. This can be useful if something else (for example, a firewall’s port
forwarding configuration) is causing connections to reach us.

IPv4Only
If the address is absent, or resolves to both an IPv4 and an IPv6 address, only listen to the
IPv4 address.

IPv6Only
If the address is absent, or resolves to both an IPv4 and an IPv6 address, only listen to the
IPv6 address.

For obvious reasons, NoAdvertise and NoListen are mutually exclusive, and IPv4Only and IPv6Only are
mutually exclusive.

PortForwarding 0|1
Attempt to automatically forward the DirPort and ORPort on a NAT router connecting this Tor server to
the Internet. If set, Tor will try both NAT-PMP (common on Apple routers) and UPnP (common on routers
from other manufacturers). (Default: 0)

PortForwardingHelper filename|pathname
If PortForwarding is set, use this executable to configure the forwarding. If set to a filename, the
system path will be searched for the executable. If set to a path, only the specified path will be
executed. (Default: tor-fw-helper)

PublishServerDescriptor 0|1|v3|bridge,...
This option specifies which descriptors Tor will publish when acting as a relay. You can choose
multiple arguments, separated by commas.

If this option is set to 0, Tor will not publish its descriptors to any directories. (This is useful
if you’re testing out your server, or if you’re using a Tor controller that handles directory
publishing for you.) Otherwise, Tor will publish its descriptors of all type(s) specified. The
default is "1", which means "if running as a relay or bridge, publish descriptors to the appropriate
authorities". Other possibilities are "v3", meaning "publish as if you’re a relay", and "bridge",
meaning "publish as if you’re a bridge".

ShutdownWaitLength NUM
When we get a SIGINT and we’re a server, we begin shutting down: we close listeners and start
refusing new circuits. After NUM seconds, we exit. If we get a second SIGINT, we exit immediately.
(Default: 30 seconds)

SSLKeyLifetime N minutes|hours|days|weeks
When creating a link certificate for our outermost SSL handshake, set its lifetime to this amount of
time. If set to 0, Tor will choose some reasonable random defaults. (Default: 0)

HeartbeatPeriod N minutes|hours|days|weeks
Log a heartbeat message every HeartbeatPeriod seconds. This is a log level notice message, designed
to let you know your Tor server is still alive and doing useful things. Settings this to 0 will
disable the heartbeat. Otherwise, it must be at least 30 minutes. (Default: 6 hours)

AccountingMax N bytes|KBytes|MBytes|GBytes|TBytes|KBits|MBits|GBits|TBits
Limits the max number of bytes sent and received within a set time period using a given calculation
rule (see: AccountingStart, AccountingRule). Useful if you need to stay under a specific bandwidth.
By default, the number used for calculation is the max of either the bytes sent or received. For
example, with AccountingMax set to 1 GByte, a server could send 900 MBytes and receive 800 MBytes and
continue running. It will only hibernate once one of the two reaches 1 GByte. This can be changed to
use the sum of the both bytes received and sent by setting the AccountingRule option to "sum" (total
bandwidth in/out). When the number of bytes remaining gets low, Tor will stop accepting new
connections and circuits. When the number of bytes is exhausted, Tor will hibernate until some time
in the next accounting period. To prevent all servers from waking at the same time, Tor will also
wait until a random point in each period before waking up. If you have bandwidth cost issues,
enabling hibernation is preferable to setting a low bandwidth, since it provides users with a
collection of fast servers that are up some of the time, which is more useful than a set of slow
servers that are always "available".

AccountingRule sum|max|in|out
How we determine when our AccountingMax has been reached (when we should hibernate) during a time
interval. Set to "max" to calculate using the higher of either the sent or received bytes (this is
the default functionality). Set to "sum" to calculate using the sent plus received bytes. Set to "in"
to calculate using only the received bytes. Set to "out" to calculate using only the sent bytes.
(Default: max)

AccountingStart day|week|month [day] HH:MM
Specify how long accounting periods last. If month is given, each accounting period runs from the
time HH:MM on the dayth day of one month to the same day and time of the next. (The day must be
between 1 and 28.) If week is given, each accounting period runs from the time HH:MM of the dayth day
of one week to the same day and time of the next week, with Monday as day 1 and Sunday as day 7. If
day is given, each accounting period runs from the time HH:MM each day to the same time on the next
day. All times are local, and given in 24-hour time. (Default: "month 1 0:00")

RefuseUnknownExits 0|1|auto
Prevent nodes that don’t appear in the consensus from exiting using this relay. If the option is 1,
we always block exit attempts from such nodes; if it’s 0, we never do, and if the option is "auto",
then we do whatever the authorities suggest in the consensus (and block if the consensus is quiet on
the issue). (Default: auto)

ServerDNSResolvConfFile filename
Overrides the default DNS configuration with the configuration in filename. The file format is the
same as the standard Unix "resolv.conf" file (7). This option, like all other ServerDNS options, only
affects name lookups that your server does on behalf of clients. (Defaults to use the system DNS
configuration.)

ServerDNSAllowBrokenConfig 0|1
If this option is false, Tor exits immediately if there are problems parsing the system DNS
configuration or connecting to nameservers. Otherwise, Tor continues to periodically retry the system
nameservers until it eventually succeeds. (Default: 1)

ServerDNSSearchDomains 0|1
If set to 1, then we will search for addresses in the local search domain. For example, if this
system is configured to believe it is in "example.com", and a client tries to connect to "www", the
client will be connected to "www.example.com". This option only affects name lookups that your server
does on behalf of clients. (Default: 0)

ServerDNSDetectHijacking 0|1
When this option is set to 1, we will test periodically to determine whether our local nameservers
have been configured to hijack failing DNS requests (usually to an advertising site). If they are, we
will attempt to correct this. This option only affects name lookups that your server does on behalf
of clients. (Default: 1)

ServerDNSTestAddresses hostname,hostname,...
When we’re detecting DNS hijacking, make sure that these valid addresses aren’t getting redirected.
If they are, then our DNS is completely useless, and we’ll reset our exit policy to "reject *:*".
This option only affects name lookups that your server does on behalf of clients. (Default:
"www.google.com, www.mit.edu, www.yahoo.com, www.slashdot.org")

ServerDNSAllowNonRFC953Hostnames 0|1
When this option is disabled, Tor does not try to resolve hostnames containing illegal characters
(like @ and :) rather than sending them to an exit node to be resolved. This helps trap accidental
attempts to resolve URLs and so on. This option only affects name lookups that your server does on
behalf of clients. (Default: 0)

BridgeRecordUsageByCountry 0|1
When this option is enabled and BridgeRelay is also enabled, and we have GeoIP data, Tor keeps a
per-country count of how many client addresses have contacted it so that it can help the bridge
authority guess which countries have blocked access to it. (Default: 1)

ServerDNSRandomizeCase 0|1
When this option is set, Tor sets the case of each character randomly in outgoing DNS requests, and
makes sure that the case matches in DNS replies. This so-called "0x20 hack" helps resist some types
of DNS poisoning attack. For more information, see "Increased DNS Forgery Resistance through 0x20-Bit
Encoding". This option only affects name lookups that your server does on behalf of clients.
(Default: 1)

GeoIPFile filename
A filename containing IPv4 GeoIP data, for use with by-country statistics.

GeoIPv6File filename
A filename containing IPv6 GeoIP data, for use with by-country statistics.

CellStatistics 0|1
Relays only. When this option is enabled, Tor collects statistics about cell processing (i.e. mean
time a cell is spending in a queue, mean number of cells in a queue and mean number of processed
cells per circuit) and writes them into disk every 24 hours. Onion router operators may use the
statistics for performance monitoring. If ExtraInfoStatistics is enabled, it will published as part
of extra-info document. (Default: 0)

PaddingStatistics 0|1
Relays only. When this option is enabled, Tor collects statistics for padding cells sent and received
by this relay, in addition to total cell counts. These statistics are rounded, and omitted if traffic
is low. This information is important for load balancing decisions related to padding. (Default: 1)

DirReqStatistics 0|1
Relays and bridges only. When this option is enabled, a Tor directory writes statistics on the number
and response time of network status requests to disk every 24 hours. Enables relay and bridge
operators to monitor how much their server is being used by clients to learn about Tor network. If
ExtraInfoStatistics is enabled, it will published as part of extra-info document. (Default: 1)

EntryStatistics 0|1
Relays only. When this option is enabled, Tor writes statistics on the number of directly connecting
clients to disk every 24 hours. Enables relay operators to monitor how much inbound traffic that
originates from Tor clients passes through their server to go further down the Tor network. If
ExtraInfoStatistics is enabled, it will be published as part of extra-info document. (Default: 0)

ExitPortStatistics 0|1
Exit relays only. When this option is enabled, Tor writes statistics on the number of relayed bytes
and opened stream per exit port to disk every 24 hours. Enables exit relay operators to measure and
monitor amounts of traffic that leaves Tor network through their exit node. If ExtraInfoStatistics is
enabled, it will be published as part of extra-info document. (Default: 0)

ConnDirectionStatistics 0|1
Relays only. When this option is enabled, Tor writes statistics on the amounts of traffic it passes
between itself and other relays to disk every 24 hours. Enables relay operators to monitor how much
their relay is being used as middle node in the circuit. If ExtraInfoStatistics is enabled, it will
be published as part of extra-info document. (Default: 0)

HiddenServiceStatistics 0|1
Relays only. When this option is enabled, a Tor relay writes obfuscated statistics on its role as
hidden-service directory, introduction point, or rendezvous point to disk every 24 hours. If
ExtraInfoStatistics is also enabled, these statistics are further published to the directory
authorities. (Default: 1)

ExtraInfoStatistics 0|1
When this option is enabled, Tor includes previously gathered statistics in its extra-info documents
that it uploads to the directory authorities. (Default: 1)

ExtendAllowPrivateAddresses 0|1
When this option is enabled, Tor will connect to relays on localhost, RFC1918 addresses, and so on.
In particular, Tor will make direct OR connections, and Tor routers allow EXTEND requests, to these
private addresses. (Tor will always allow connections to bridges, proxies, and pluggable transports
configured on private addresses.) Enabling this option can create security issues; you should
probably leave it off. (Default: 0)

MaxMemInQueues N bytes|KB|MB|GB
This option configures a threshold above which Tor will assume that it needs to stop queueing or
buffering data because it’s about to run out of memory. If it hits this threshold, it will begin
killing circuits until it has recovered at least 10% of this memory. Do not set this option too low,
or your relay may be unreliable under load. This option only affects some queues, so the actual
process size will be larger than this. If this option is set to 0, Tor will try to pick a reasonable
default based on your system’s physical memory. (Default: 0)

DisableOOSCheck 0|1
This option disables the code that closes connections when Tor notices that it is running low on
sockets. Right now, it is on by default, since the existing out-of-sockets mechanism tends to kill OR
connections more than it should. (Default: 1)

SigningKeyLifetime N days|weeks|months
For how long should each Ed25519 signing key be valid? Tor uses a permanent master identity key that
can be kept offline, and periodically generates new "signing" keys that it uses online. This option
configures their lifetime. (Default: 30 days)

OfflineMasterKey 0|1
If non-zero, the Tor relay will never generate or load its master secret key. Instead, you’ll have to
use "tor --keygen" to manage the permanent ed25519 master identity key, as well as the corresponding
temporary signing keys and certificates. (Default: 0)

DIRECTORY SERVER OPTIONS

The following options are useful only for directory servers. (Relays with enough bandwidth automatically
become directory servers; see DirCache for details.)

DirPortFrontPage FILENAME
When this option is set, it takes an HTML file and publishes it as "/" on the DirPort. Now relay
operators can provide a disclaimer without needing to set up a separate webserver. There’s a sample
disclaimer in contrib/operator-tools/tor-exit-notice.html.

DirPort [address:]PORT|auto [flags]
If this option is nonzero, advertise the directory service on this port. Set it to "auto" to have Tor
pick a port for you. This option can occur more than once, but only one advertised DirPort is
supported: all but one DirPort must have the NoAdvertise flag set. (Default: 0)

The same flags are supported here as are supported by ORPort.

DirPolicy policy,policy,...
Set an entrance policy for this server, to limit who can connect to the directory ports. The policies
have the same form as exit policies above, except that port specifiers are ignored. Any address not
matched by some entry in the policy is accepted.

DirCache 0|1
When this option is set, Tor caches all current directory documents and accepts client requests for
them. Setting DirPort is not required for this, because clients connect via the ORPort by default.
Setting either DirPort or BridgeRelay and setting DirCache to 0 is not supported. (Default: 1)

MaxConsensusAgeForDiffs N minutes|hours|days|weeks
When this option is nonzero, Tor caches will not try to generate consensus diffs for any consensus
older than this amount of time. If this option is set to zero, Tor will pick a reasonable default
from the current networkstatus document. You should not set this option unless your cache is severely
low on disk space or CPU. If you need to set it, keeping it above 3 or 4 hours will help clients much
more than setting it to zero. (Default: 0)

DIRECTORY AUTHORITY SERVER OPTIONS

The following options enable operation as a directory authority, and control how Tor behaves as a
directory authority. You should not need to adjust any of them if you’re running a regular relay or exit
server on the public Tor network.

AuthoritativeDirectory 0|1
When this option is set to 1, Tor operates as an authoritative directory server. Instead of caching
the directory, it generates its own list of good servers, signs it, and sends that to the clients.
Unless the clients already have you listed as a trusted directory, you probably do not want to set
this option.

V3AuthoritativeDirectory 0|1
When this option is set in addition to AuthoritativeDirectory, Tor generates version 3 network
statuses and serves descriptors, etc as described in dir-spec.txt file of torspec (for Tor clients
and servers running at least 0.2.0.x).

VersioningAuthoritativeDirectory 0|1
When this option is set to 1, Tor adds information on which versions of Tor are still believed safe
for use to the published directory. Each version 1 authority is automatically a versioning authority;
version 2 authorities provide this service optionally. See RecommendedVersions,
RecommendedClientVersions, and RecommendedServerVersions.

RecommendedVersions STRING
STRING is a comma-separated list of Tor versions currently believed to be safe. The list is included
in each directory, and nodes which pull down the directory learn whether they need to upgrade. This
option can appear multiple times: the values from multiple lines are spliced together. When this is
set then VersioningAuthoritativeDirectory should be set too.

RecommendedPackages PACKAGENAME VERSION URL DIGESTTYPE=DIGEST
Adds "package" line to the directory authority’s vote. This information is used to vote on the
correct URL and digest for the released versions of different Tor-related packages, so that the
consensus can certify them. This line may appear any number of times.

RecommendedClientVersions STRING
STRING is a comma-separated list of Tor versions currently believed to be safe for clients to use.
This information is included in version 2 directories. If this is not set then the value of
RecommendedVersions is used. When this is set then VersioningAuthoritativeDirectory should be set
too.

BridgeAuthoritativeDir 0|1
When this option is set in addition to AuthoritativeDirectory, Tor accepts and serves server
descriptors, but it caches and serves the main networkstatus documents rather than generating its
own. (Default: 0)

MinUptimeHidServDirectoryV2 N seconds|minutes|hours|days|weeks
Minimum uptime of a v2 hidden service directory to be accepted as such by authoritative directories.
(Default: 25 hours)

RecommendedServerVersions STRING
STRING is a comma-separated list of Tor versions currently believed to be safe for servers to use.
This information is included in version 2 directories. If this is not set then the value of
RecommendedVersions is used. When this is set then VersioningAuthoritativeDirectory should be set
too.

ConsensusParams STRING
STRING is a space-separated list of key=value pairs that Tor will include in the "params" line of its
networkstatus vote.

DirAllowPrivateAddresses 0|1
If set to 1, Tor will accept server descriptors with arbitrary "Address" elements. Otherwise, if the
address is not an IP address or is a private IP address, it will reject the server descriptor.
Additionally, Tor will allow exit policies for private networks to fulfill Exit flag requirements.
(Default: 0)

AuthDirBadExit AddressPattern...
Authoritative directories only. A set of address patterns for servers that will be listed as bad
exits in any network status document this authority publishes, if AuthDirListBadExits is set.

(The address pattern syntax here and in the options below is the same as for exit policies, except
that you don’t need to say "accept" or "reject", and ports are not needed.)

AuthDirInvalid AddressPattern...
Authoritative directories only. A set of address patterns for servers that will never be listed as
"valid" in any network status document that this authority publishes.

AuthDirReject AddressPattern...
Authoritative directories only. A set of address patterns for servers that will never be listed at
all in any network status document that this authority publishes, or accepted as an OR address in any
descriptor submitted for publication by this authority.

AuthDirBadExitCCs CC,...

AuthDirInvalidCCs CC,...

AuthDirRejectCCs CC,...
Authoritative directories only. These options contain a comma-separated list of country codes such
that any server in one of those country codes will be marked as a bad exit/invalid for use, or
rejected entirely.

AuthDirListBadExits 0|1
Authoritative directories only. If set to 1, this directory has some opinion about which nodes are
unsuitable as exit nodes. (Do not set this to 1 unless you plan to list non-functioning exits as bad;
otherwise, you are effectively voting in favor of every declared exit as an exit.)

AuthDirMaxServersPerAddr NUM
Authoritative directories only. The maximum number of servers that we will list as acceptable on a
single IP address. Set this to "0" for "no limit". (Default: 2)

AuthDirPinKeys 0|1
Authoritative directories only. If non-zero, do not allow any relay to publish a descriptor if any
other relay has reserved its <Ed25519,RSA> identity keypair. In all cases, Tor records every keypair
it accepts in a journal if it is new, or if it differs from the most recently accepted pinning for
one of the keys it contains. (Default: 1)

AuthDirSharedRandomness 0|1
Authoritative directories only. Switch for the shared random protocol. If zero, the authority won’t
participate in the protocol. If non-zero (default), the flag "shared-rand-participate" is added to
the authority vote indicating participation in the protocol. (Default: 1)

AuthDirTestEd25519LinkKeys 0|1
Authoritative directories only. If this option is set to 0, then we treat relays as "Running" if
their RSA key is correct when we probe them, regardless of their Ed25519 key. We should only ever set
this option to 0 if there is some major bug in Ed25519 link authentication that causes us to label
all the relays as not Running. (Default: 1)

BridgePassword Password
If set, contains an HTTP authenticator that tells a bridge authority to serve all requested bridge
information. Used by the (only partially implemented) "bridge community" design, where a community of
bridge relay operators all use an alternate bridge directory authority, and their target user
audience can periodically fetch the list of available community bridges to stay up-to-date. (Default:
not set)

V3AuthVotingInterval N minutes|hours
V3 authoritative directories only. Configures the server’s preferred voting interval. Note that
voting will actually happen at an interval chosen by consensus from all the authorities' preferred
intervals. This time SHOULD divide evenly into a day. (Default: 1 hour)

V3AuthVoteDelay N minutes|hours
V3 authoritative directories only. Configures the server’s preferred delay between publishing its
vote and assuming it has all the votes from all the other authorities. Note that the actual time used
is not the server’s preferred time, but the consensus of all preferences. (Default: 5 minutes)

V3AuthDistDelay N minutes|hours
V3 authoritative directories only. Configures the server’s preferred delay between publishing its
consensus and signature and assuming it has all the signatures from all the other authorities. Note
that the actual time used is not the server’s preferred time, but the consensus of all preferences.
(Default: 5 minutes)

V3AuthNIntervalsValid NUM
V3 authoritative directories only. Configures the number of VotingIntervals for which each consensus
should be valid for. Choosing high numbers increases network partitioning risks; choosing low numbers
increases directory traffic. Note that the actual number of intervals used is not the server’s
preferred number, but the consensus of all preferences. Must be at least 2. (Default: 3)

V3BandwidthsFile FILENAME
V3 authoritative directories only. Configures the location of the bandwidth-authority generated file
storing information on relays' measured bandwidth capacities. (Default: unset)

V3AuthUseLegacyKey 0|1
If set, the directory authority will sign consensuses not only with its own signing key, but also
with a "legacy" key and certificate with a different identity. This feature is used to migrate
directory authority keys in the event of a compromise. (Default: 0)

RephistTrackTime N seconds|minutes|hours|days|weeks
Tells an authority, or other node tracking node reliability and history, that fine-grained
information about nodes can be discarded when it hasn’t changed for a given amount of time. (Default:
24 hours)

AuthDirHasIPv6Connectivity 0|1
Authoritative directories only. When set to 0, OR ports with an IPv6 address are being accepted
without reachability testing. When set to 1, IPv6 OR ports are being tested just like IPv4 OR ports.
(Default: 0)

MinMeasuredBWsForAuthToIgnoreAdvertised N
A total value, in abstract bandwidth units, describing how much measured total bandwidth an authority
should have observed on the network before it will treat advertised bandwidths as wholly unreliable.
(Default: 500)

HIDDEN SERVICE OPTIONS

The following options are used to configure a hidden service.

HiddenServiceDir DIRECTORY
Store data files for a hidden service in DIRECTORY. Every hidden service must have a separate
directory. You may use this option multiple times to specify multiple services. If DIRECTORY does not
exist, Tor will create it. (Note: in current versions of Tor, if DIRECTORY is a relative path, it
will be relative to the current working directory of Tor instance, not to its DataDirectory. Do not
rely on this behavior; it is not guaranteed to remain the same in future versions.)

HiddenServicePort VIRTPORT [TARGET]
Configure a virtual port VIRTPORT for a hidden service. You may use this option multiple times; each
time applies to the service using the most recent HiddenServiceDir. By default, this option maps the
virtual port to the same port on 127.0.0.1 over TCP. You may override the target port, address, or
both by specifying a target of addr, port, addr:port, or unix:path. (You can specify an IPv6 target
as [addr]:port. Unix paths may be quoted, and may use standard C escapes.) You may also have multiple
lines with the same VIRTPORT: when a user connects to that VIRTPORT, one of the TARGETs from those
lines will be chosen at random.

PublishHidServDescriptors 0|1
If set to 0, Tor will run any hidden services you configure, but it won’t advertise them to the
rendezvous directory. This option is only useful if you’re using a Tor controller that handles
hidserv publishing for you. (Default: 1)

HiddenServiceVersion version,version,...
A list of rendezvous service descriptor versions to publish for the hidden service. Currently,
versions 2 and 3 are supported. (Default: 2)

HiddenServiceAuthorizeClient auth-type client-name,client-name,...
If configured, the hidden service is accessible for authorized clients only. The auth-type can either
be 'basic' for a general-purpose authorization protocol or 'stealth' for a less scalable protocol
that also hides service activity from unauthorized clients. Only clients that are listed here are
authorized to access the hidden service. Valid client names are 1 to 16 characters long and only use
characters in A-Za-z0-9+-_ (no spaces). If this option is set, the hidden service is not accessible
for clients without authorization any more. Generated authorization data can be found in the hostname
file. Clients need to put this authorization data in their configuration file using HidServAuth.

HiddenServiceAllowUnknownPorts 0|1
If set to 1, then connections to unrecognized ports do not cause the current hidden service to close
rendezvous circuits. (Setting this to 0 is not an authorization mechanism; it is instead meant to be
a mild inconvenience to port-scanners.) (Default: 0)

HiddenServiceMaxStreams N
The maximum number of simultaneous streams (connections) per rendezvous circuit. The maximum value
allowed is 65535. (Setting this to 0 will allow an unlimited number of simultanous streams.)
(Default: 0)

HiddenServiceMaxStreamsCloseCircuit 0|1
If set to 1, then exceeding HiddenServiceMaxStreams will cause the offending rendezvous circuit to be
torn down, as opposed to stream creation requests that exceed the limit being silently ignored.
(Default: 0)

RendPostPeriod N seconds|minutes|hours|days|weeks
Every time the specified period elapses, Tor uploads any rendezvous service descriptors to the
directory servers. This information is also uploaded whenever it changes. Minimum value allowed is 10
minutes and maximum is 3.5 days. (Default: 1 hour)

HiddenServiceDirGroupReadable 0|1
If this option is set to 1, allow the filesystem group to read the hidden service directory and
hostname file. If the option is set to 0, only owner is able to read the hidden service directory.
(Default: 0) Has no effect on Windows.

HiddenServiceNumIntroductionPoints NUM
Number of introduction points the hidden service will have. You can’t have more than 10 for v2
service and 20 for v3. (Default: 3)

HiddenServiceSingleHopMode 0|1
Experimental - Non Anonymous Hidden Services on a tor instance in HiddenServiceSingleHopMode make
one-hop (direct) circuits between the onion service server, and the introduction and rendezvous
points. (Onion service descriptors are still posted using 3-hop paths, to avoid onion service
directories blocking the service.) This option makes every hidden service instance hosted by a tor
instance a Single Onion Service. One-hop circuits make Single Onion servers easily locatable, but
clients remain location-anonymous. However, the fact that a client is accessing a Single Onion rather
than a Hidden Service may be statistically distinguishable.

WARNING: Once a hidden service directory has been used by a tor instance in
HiddenServiceSingleHopMode, it can NEVER be used again for a hidden service. It is best practice to
create a new hidden service directory, key, and address for each new Single Onion Service and Hidden
Service. It is not possible to run Single Onion Services and Hidden Services from the same tor
instance: they should be run on different servers with different IP addresses.

HiddenServiceSingleHopMode requires HiddenServiceNonAnonymousMode to be set to 1. Since a Single
Onion service is non-anonymous, you can not configure a SOCKSPort on a tor instance that is running
in HiddenServiceSingleHopMode. Can not be changed while tor is running. (Default: 0)

HiddenServiceNonAnonymousMode 0|1
Makes hidden services non-anonymous on this tor instance. Allows the non-anonymous
HiddenServiceSingleHopMode. Enables direct connections in the server-side hidden service protocol. If
you are using this option, you need to disable all client-side services on your Tor instance,
including setting SOCKSPort to "0". Can not be changed while tor is running. (Default: 0)

DENIAL OF SERVICE MITIGATION OPTIONS

The following options are useful only for a public relay. They control the Denial of Service mitigation
subsystem.

DoSCircuitCreationEnabled 0|1|auto
Enable circuit creation DoS mitigation. If enabled, tor will cache client IPs along with statistics
in order to detect circuit DoS attacks. If an address is positively identified, tor will activate
defenses against the address. See the DoSCircuitCreationDefenseType option for more details. This is
a client to relay detection only. "auto" means use the consensus parameter. If not defined in the
consensus, the value is 0. (Default: auto)

DoSCircuitCreationMinConnections NUM
Minimum threshold of concurrent connections before a client address can be flagged as executing a
circuit creation DoS. In other words, once a client address reaches the circuit rate and has a
minimum of NUM concurrent connections, a detection is positive. "0" means use the consensus
parameter. If not defined in the consensus, the value is 3. (Default: 0)

DoSCircuitCreationRate NUM
The allowed circuit creation rate per second applied per client IP address. If this option is 0, it
obeys a consensus parameter. If not defined in the consensus, the value is 3. (Default: 0)

DoSCircuitCreationBurst NUM
The allowed circuit creation burst per client IP address. If the circuit rate and the burst are
reached, a client is marked as executing a circuit creation DoS. "0" means use the consensus
parameter. If not defined in the consensus, the value is 90. (Default: 0)

DoSCircuitCreationDefenseType NUM
This is the type of defense applied to a detected client address. The possible values are:

1: No defense.
2: Refuse circuit creation for the DoSCircuitCreationDefenseTimePeriod period of time.

"0" means use the consensus parameter. If not defined in the consensus,
the value is 2.
(Default: 0)

DoSCircuitCreationDefenseTimePeriod N seconds|minutes|hours
The base time period in seconds that the DoS defense is activated for. The actual value is selected
randomly for each activation from N+1 to 3/2 * N. "0" means use the consensus parameter. If not
defined in the consensus, the value is 3600 seconds (1 hour). (Default: 0)

DoSConnectionEnabled 0|1|auto
Enable the connection DoS mitigation. For client address only, this allows tor to mitigate against
large number of concurrent connections made by a single IP address. "auto" means use the consensus
parameter. If not defined in the consensus, the value is 0. (Default: auto)

DoSConnectionMaxConcurrentCount NUM
The maximum threshold of concurrent connection from a client IP address. Above this limit, a defense
selected by DoSConnectionDefenseType is applied. "0" means use the consensus parameter. If not
defined in the consensus, the value is 100. (Default: 0)

DoSConnectionDefenseType NUM
This is the type of defense applied to a detected client address for the connection mitigation. The
possible values are:

1: No defense.
2: Immediately close new connections.

"0" means use the consensus parameter. If not defined in the consensus,
the value is 2.
(Default: 0)

DoSRefuseSingleHopClientRendezvous 0|1|auto
Refuse establishment of rendezvous points for single hop clients. In other words, if a client
directly connects to the relay and sends an ESTABLISH_RENDEZVOUS cell, it is silently dropped. "auto"
means use the consensus parameter. If not defined in the consensus, the value is 0. (Default: auto)

TESTING NETWORK OPTIONS

The following options are used for running a testing Tor network.

TestingTorNetwork 0|1
If set to 1, Tor adjusts default values of the configuration options below, so that it is easier to
set up a testing Tor network. May only be set if non-default set of DirAuthorities is set. Cannot be
unset while Tor is running. (Default: 0)

ServerDNSAllowBrokenConfig 1
DirAllowPrivateAddresses 1
EnforceDistinctSubnets 0
AssumeReachable 1
AuthDirMaxServersPerAddr 0
AuthDirMaxServersPerAuthAddr 0
ClientBootstrapConsensusAuthorityDownloadSchedule 0, 2,
4 (for 40 seconds), 8, 16, 32, 60
ClientBootstrapConsensusFallbackDownloadSchedule 0, 1,
4 (for 40 seconds), 8, 16, 32, 60
ClientBootstrapConsensusAuthorityOnlyDownloadSchedule 0, 1,
4 (for 40 seconds), 8, 16, 32, 60
ClientBootstrapConsensusMaxDownloadTries 80
ClientBootstrapConsensusAuthorityOnlyMaxDownloadTries 80
ClientDNSRejectInternalAddresses 0
ClientRejectInternalAddresses 0
CountPrivateBandwidth 1
ExitPolicyRejectPrivate 0
ExtendAllowPrivateAddresses 1
V3AuthVotingInterval 5 minutes
V3AuthVoteDelay 20 seconds
V3AuthDistDelay 20 seconds
MinUptimeHidServDirectoryV2 0 seconds
TestingV3AuthInitialVotingInterval 5 minutes
TestingV3AuthInitialVoteDelay 20 seconds
TestingV3AuthInitialDistDelay 20 seconds
TestingAuthDirTimeToLearnReachability 0 minutes
TestingEstimatedDescriptorPropagationTime 0 minutes
TestingServerDownloadSchedule 0, 0, 0, 5, 10, 15, 20, 30, 60
TestingClientDownloadSchedule 0, 0, 5, 10, 15, 20, 30, 60
TestingServerConsensusDownloadSchedule 0, 0, 5, 10, 15, 20, 30, 60
TestingClientConsensusDownloadSchedule 0, 0, 5, 10, 15, 20, 30, 60
TestingBridgeDownloadSchedule 10, 30, 60
TestingBridgeBootstrapDownloadSchedule 0, 0, 5, 10, 15, 20, 30, 60
TestingClientMaxIntervalWithoutRequest 5 seconds
TestingDirConnectionMaxStall 30 seconds
TestingConsensusMaxDownloadTries 80
TestingDescriptorMaxDownloadTries 80
TestingMicrodescMaxDownloadTries 80
TestingCertMaxDownloadTries 80
TestingEnableConnBwEvent 1
TestingEnableCellStatsEvent 1
TestingEnableTbEmptyEvent 1

TestingV3AuthInitialVotingInterval N minutes|hours
Like V3AuthVotingInterval, but for initial voting interval before the first consensus has been
created. Changing this requires that TestingTorNetwork is set. (Default: 30 minutes)

TestingV3AuthInitialVoteDelay N minutes|hours
Like V3AuthVoteDelay, but for initial voting interval before the first consensus has been created.
Changing this requires that TestingTorNetwork is set. (Default: 5 minutes)

TestingV3AuthInitialDistDelay N minutes|hours
Like V3AuthDistDelay, but for initial voting interval before the first consensus has been created.
Changing this requires that TestingTorNetwork is set. (Default: 5 minutes)

TestingV3AuthVotingStartOffset N seconds|minutes|hours
Directory authorities offset voting start time by this much. Changing this requires that
TestingTorNetwork is set. (Default: 0)

TestingAuthDirTimeToLearnReachability N minutes|hours
After starting as an authority, do not make claims about whether routers are Running until this much
time has passed. Changing this requires that TestingTorNetwork is set. (Default: 30 minutes)

TestingEstimatedDescriptorPropagationTime N minutes|hours
Clients try downloading server descriptors from directory caches after this time. Changing this
requires that TestingTorNetwork is set. (Default: 10 minutes)

TestingServerDownloadSchedule N,N,...
Schedule for when servers should download things in general. Changing this requires that
TestingTorNetwork is set. (Default: 0, 0, 0, 60, 60, 120, 300, 900, 2147483647)

TestingClientDownloadSchedule N,N,...
Schedule for when clients should download things in general. Changing this requires that
TestingTorNetwork is set. (Default: 0, 0, 60, 300, 600, 2147483647)

TestingServerConsensusDownloadSchedule N,N,...
Schedule for when servers should download consensuses. Changing this requires that TestingTorNetwork
is set. (Default: 0, 0, 60, 300, 600, 1800, 1800, 1800, 1800, 1800, 3600, 7200)

TestingClientConsensusDownloadSchedule N,N,...
Schedule for when clients should download consensuses. Changing this requires that TestingTorNetwork
is set. (Default: 0, 0, 60, 300, 600, 1800, 3600, 3600, 3600, 10800, 21600, 43200)

TestingBridgeDownloadSchedule N,N,...
Schedule for when clients should download each bridge descriptor when they know that one or more of
their configured bridges are running. Changing this requires that TestingTorNetwork is set. (Default:
10800, 25200, 54000, 111600, 262800)

TestingBridgeBootstrapDownloadSchedule N,N,...
Schedule for when clients should download each bridge descriptor when they have just started, or when
they can not contact any of their bridges. Changing this requires that TestingTorNetwork is set.
(Default: 0, 30, 90, 600, 3600, 10800, 25200, 54000, 111600, 262800)

TestingClientMaxIntervalWithoutRequest N seconds|minutes
When directory clients have only a few descriptors to request, they batch them until they have more,
or until this amount of time has passed. Changing this requires that TestingTorNetwork is set.
(Default: 10 minutes)

TestingDirConnectionMaxStall N seconds|minutes
Let a directory connection stall this long before expiring it. Changing this requires that
TestingTorNetwork is set. (Default: 5 minutes)

TestingConsensusMaxDownloadTries NUM
Try this many times to download a consensus before giving up. Changing this requires that
TestingTorNetwork is set. (Default: 8)

TestingDescriptorMaxDownloadTries NUM
Try this often to download a server descriptor before giving up. Changing this requires that
TestingTorNetwork is set. (Default: 8)

TestingMicrodescMaxDownloadTries NUM
Try this often to download a microdesc descriptor before giving up. Changing this requires that
TestingTorNetwork is set. (Default: 8)

TestingCertMaxDownloadTries NUM
Try this often to download a v3 authority certificate before giving up. Changing this requires that
TestingTorNetwork is set. (Default: 8)

TestingDirAuthVoteExit node,node,...
A list of identity fingerprints, country codes, and address patterns of nodes to vote Exit for
regardless of their uptime, bandwidth, or exit policy. See the ExcludeNodes option for more
information on how to specify nodes.

In order for this option to have any effect, TestingTorNetwork has to be set. See the ExcludeNodes
option for more information on how to specify nodes.

TestingDirAuthVoteExitIsStrict 0|1
If True (1), a node will never receive the Exit flag unless it is specified in the
TestingDirAuthVoteExit list, regardless of its uptime, bandwidth, or exit policy.

In order for this option to have any effect, TestingTorNetwork has to be set.

TestingDirAuthVoteGuard node,node,...
A list of identity fingerprints and country codes and address patterns of nodes to vote Guard for
regardless of their uptime and bandwidth. See the ExcludeNodes option for more information on how to
specify nodes.

In order for this option to have any effect, TestingTorNetwork has to be set.

TestingDirAuthVoteGuardIsStrict 0|1
If True (1), a node will never receive the Guard flag unless it is specified in the
TestingDirAuthVoteGuard list, regardless of its uptime and bandwidth.

In order for this option to have any effect, TestingTorNetwork has to be set.

TestingDirAuthVoteHSDir node,node,...
A list of identity fingerprints and country codes and address patterns of nodes to vote HSDir for
regardless of their uptime and DirPort. See the ExcludeNodes option for more information on how to
specify nodes.

In order for this option to have any effect, TestingTorNetwork must be set.

TestingDirAuthVoteHSDirIsStrict 0|1
If True (1), a node will never receive the HSDir flag unless it is specified in the
TestingDirAuthVoteHSDir list, regardless of its uptime and DirPort.

In order for this option to have any effect, TestingTorNetwork has to be set.

TestingEnableConnBwEvent 0|1
If this option is set, then Tor controllers may register for CONN_BW events. Changing this requires
that TestingTorNetwork is set. (Default: 0)

TestingEnableCellStatsEvent 0|1
If this option is set, then Tor controllers may register for CELL_STATS events. Changing this
requires that TestingTorNetwork is set. (Default: 0)

TestingEnableTbEmptyEvent 0|1
If this option is set, then Tor controllers may register for TB_EMPTY events. Changing this requires
that TestingTorNetwork is set. (Default: 0)

TestingLinkKeySlop N seconds|minutes|hours

TestingAuthKeySlop N seconds|minutes|hours

TestingSigningKeySlop N seconds|minutes|hours
How early before the official expiration of a an Ed25519 signing key do we replace it and issue a new
key? (Default: 3 hours for link and auth; 1 day for signing.)

NON-PERSISTENT OPTIONS

       These options are not saved to the torrc file by the "SAVECONF" controller command. Other options of this
       type are documented in control-spec.txt, section 5.4. End-users should mostly ignore them.

       __ControlPort, __DirPort, __DNSPort, __ExtORPort, __NATDPort, __ORPort, __SocksPort, \_\_TransPort
           These underscore-prefixed options are variants of the regular Port options. They behave the same,
           except they are not saved to the torrc file by the controller’s SAVECONF command.

SIGNALS

       Tor catches the following signals:

       SIGTERM
           Tor will catch this, clean up and sync to disk if necessary, and exit.

       SIGINT
           Tor clients behave as with SIGTERM; but Tor servers will do a controlled slow shutdown, closing
           listeners and waiting 30 seconds before exiting. (The delay can be configured with the
           ShutdownWaitLength config option.)

       SIGHUP
           The signal instructs Tor to reload its configuration (including closing and reopening logs), and kill
           and restart its helper processes if applicable.

       SIGUSR1
           Log statistics about current connections, past connections, and throughput.

       SIGUSR2
           Switch all logs to loglevel debug. You can go back to the old loglevels by sending a SIGHUP.

       SIGCHLD
           Tor receives this signal when one of its helper processes has exited, so it can clean up.

       SIGPIPE
           Tor catches this signal and ignores it.

       SIGXFSZ
           If this signal exists on your platform, Tor catches and ignores it.

FILES

/etc/tor/torrc
The configuration file, which contains "option value" pairs.

$HOME/.torrc
Fallback location for torrc, if /etc/tor/torrc is not found.

/var/lib/tor/
The tor process stores keys and other data here.

DataDirectory/cached-status/
The most recently downloaded network status document for each authority. Each file holds one such
document; the filenames are the hexadecimal identity key fingerprints of the directory authorities.
Obsolete; no longer in use.

DataDirectory/cached-certs
This file holds downloaded directory key certificates that are used to verify authenticity of
documents generated by Tor directory authorities.

DataDirectory/cached-consensus and/or cached-microdesc-consensus
The most recent consensus network status document we’ve downloaded.

DataDirectory/cached-descriptors and cached-descriptors.new
These files hold downloaded router statuses. Some routers may appear more than once; if so, the most
recently published descriptor is used. Lines beginning with @-signs are annotations that contain more
information about a given router. The ".new" file is an append-only journal; when it gets too large,
all entries are merged into a new cached-descriptors file.

DataDirectory/cached-extrainfo and cached-extrainfo.new
As "cached-descriptors", but holds optionally-downloaded "extra-info" documents. Relays use these
documents to send inessential information about statistics, bandwidth history, and network health to
the authorities. They aren’t fetched by default; see the DownloadExtraInfo option for more info.

DataDirectory/cached-microdescs and cached-microdescs.new
These files hold downloaded microdescriptors. Lines beginning with @-signs are annotations that
contain more information about a given router. The ".new" file is an append-only journal; when it
gets too large, all entries are merged into a new cached-microdescs file.

DataDirectory/cached-routers and cached-routers.new
Obsolete versions of cached-descriptors and cached-descriptors.new. When Tor can’t find the newer
files, it looks here instead.

DataDirectory/state
A set of persistent key-value mappings. These are documented in the file. These include:

• The current entry guards and their status.

• The current bandwidth accounting values.

• When the file was last written

• What version of Tor generated the state file

• A short history of bandwidth usage, as produced in the server descriptors.

DataDirectory/sr-state
Authority only. State file used to record information about the current status of the
shared-random-value voting state.

DataDirectory/diff-cache
Directory cache only. Holds older consensuses, and diffs from older consensuses to the most recent
consensus of each type, compressed in various ways. Each file contains a set of key-value arguments
decribing its contents, followed by a single NUL byte, followed by the main file contents.

DataDirectory/bw_accounting
Used to track bandwidth accounting values (when the current period starts and ends; how much has been
read and written so far this period). This file is obsolete, and the data is now stored in the
'state' file instead.

DataDirectory/control_auth_cookie
Used for cookie authentication with the controller. Location can be overridden by the CookieAuthFile
config option. Regenerated on startup. See control-spec.txt in torspec for details. Only used when
cookie authentication is enabled.

DataDirectory/lock
This file is used to prevent two Tor instances from using same data directory. If access to this file
is locked, data directory is already in use by Tor.

DataDirectory/key-pinning-journal
Used by authorities. A line-based file that records mappings between RSA1024 identity keys and
Ed25519 identity keys. Authorities enforce these mappings, so that once a relay has picked an Ed25519
key, stealing or factoring the RSA1024 key will no longer let an attacker impersonate the relay.

DataDirectory/keys/*
Only used by servers. Holds identity keys and onion keys.

DataDirectory/keys/authority_identity_key
A v3 directory authority’s master identity key, used to authenticate its signing key. Tor doesn’t use
this while it’s running. The tor-gencert program uses this. If you’re running an authority, you
should keep this key offline, and not actually put it here.

DataDirectory/keys/authority_certificate
A v3 directory authority’s certificate, which authenticates the authority’s current vote- and
consensus-signing key using its master identity key. Only directory authorities use this file.

DataDirectory/keys/authority_signing_key
A v3 directory authority’s signing key, used to sign votes and consensuses. Only directory
authorities use this file. Corresponds to the authority_certificate cert.

DataDirectory/keys/legacy_certificate
As authority_certificate: used only when V3AuthUseLegacyKey is set. See documentation for
V3AuthUseLegacyKey.

DataDirectory/keys/legacy_signing_key
As authority_signing_key: used only when V3AuthUseLegacyKey is set. See documentation for
V3AuthUseLegacyKey.

DataDirectory/keys/secret_id_key
A relay’s RSA1024 permanent identity key, including private and public components. Used to sign
router descriptors, and to sign other keys.

DataDirectory/keys/ed25519_master_id_public_key
The public part of a relay’s Ed25519 permanent identity key.

DataDirectory/keys/ed25519_master_id_secret_key
The private part of a relay’s Ed25519 permanent identity key. This key is used to sign the
medium-term ed25519 signing key. This file can be kept offline, or kept encrypted. If so, Tor will
not be able to generate new signing keys itself; you’ll need to use tor --keygen yourself to do so.

DataDirectory/keys/ed25519_signing_secret_key
The private and public components of a relay’s medium-term Ed25519 signing key. This key is
authenticated by the Ed25519 master key, in turn authenticates other keys (and router descriptors).

DataDirectory/keys/ed25519_signing_cert
The certificate which authenticates "ed25519_signing_secret_key" as having been signed by the Ed25519
master key.

DataDirectory/keys/secret_onion_key and secret_onion_key.old
A relay’s RSA1024 short-term onion key. Used to decrypt old-style ("TAP") circuit extension requests.
The ".old" file holds the previously generated key, which the relay uses to handle any requests that
were made by clients that didn’t have the new one.

DataDirectory/keys/secret_onion_key_ntor and secret_onion_key_ntor.old
A relay’s Curve25519 short-term onion key. Used to handle modern ("ntor") circuit extension requests.
The ".old" file holds the previously generated key, which the relay uses to handle any requests that
were made by clients that didn’t have the new one.

DataDirectory/fingerprint
Only used by servers. Holds the fingerprint of the server’s identity key.

DataDirectory/hashed-fingerprint
Only used by bridges. Holds the hashed fingerprint of the bridge’s identity key. (That is, the hash
of the hash of the identity key.)

DataDirectory/approved-routers
Only used by authoritative directory servers. This file lists the status of routers by their identity
fingerprint. Each line lists a status and a fingerprint separated by whitespace. See your fingerprint
file in the DataDirectory for an example line. If the status is !reject then descriptors from the
given identity (fingerprint) are rejected by this server. If it is !invalid then descriptors are
accepted but marked in the directory as not valid, that is, not recommended.

DataDirectory/v3-status-votes
Only for v3 authoritative directory servers. This file contains status votes from all the
authoritative directory servers.

DataDirectory/unverified-consensus
This file contains a network consensus document that has been downloaded, but which we didn’t have
the right certificates to check yet.

DataDirectory/unverified-microdesc-consensus
This file contains a microdescriptor-flavored network consensus document that has been downloaded,
but which we didn’t have the right certificates to check yet.

DataDirectory/unparseable-desc
Onion server descriptors that Tor was unable to parse are dumped to this file. Only used for
debugging.

DataDirectory/router-stability
Only used by authoritative directory servers. Tracks measurements for router
mean-time-between-failures so that authorities have a good idea of how to set their Stable flags.

DataDirectory/stats/dirreq-stats
Only used by directory caches and authorities. This file is used to collect directory request
statistics.

DataDirectory/stats/entry-stats
Only used by servers. This file is used to collect incoming connection statistics by Tor entry nodes.

DataDirectory/stats/bridge-stats
Only used by servers. This file is used to collect incoming connection statistics by Tor bridges.

DataDirectory/stats/exit-stats
Only used by servers. This file is used to collect outgoing connection statistics by Tor exit
routers.

DataDirectory/stats/buffer-stats
Only used by servers. This file is used to collect buffer usage history.

DataDirectory/stats/conn-stats
Only used by servers. This file is used to collect approximate connection history (number of active
connections over time).

DataDirectory/stats/hidserv-stats
Only used by servers. This file is used to collect approximate counts of what fraction of the traffic
is hidden service rendezvous traffic, and approximately how many hidden services the relay has seen.

DataDirectory/networkstatus-bridges
Only used by authoritative bridge directories. Contains information about bridges that have
self-reported themselves to the bridge authority.

DataDirectory/approved-routers
Authorities only. This file is used to configure which relays are known to be valid, invalid, and so
forth.

HiddenServiceDirectory/hostname
The <base32-encoded-fingerprint>.onion domain name for this hidden service. If the hidden service is
restricted to authorized clients only, this file also contains authorization data for all clients.

Note that clients will ignore any extra subdomains prepended to a hidden service hostname. So if you
have "xyz.onion" as your hostname, you can tell clients to connect to "www.xyz.onion" or
"irc.xyz.onion" for virtual-hosting purposes.

HiddenServiceDirectory/private_key
The private key for this hidden service.

HiddenServiceDirectory/client_keys
Authorization data for a hidden service that is only accessible by authorized clients.

HiddenServiceDirectory/onion_service_non_anonymous
This file is present if a hidden service key was created in HiddenServiceNonAnonymousMode.

BUGS

       Plenty, probably. Tor is still in development. Please report them at https://trac.torproject.org/.

AUTHORS

       Roger Dingledine [arma at mit.edu], Nick Mathewson [nickm at alum.mit.edu].

Tor                                                03/03/2018                                             TOR(1)

NAME

SYNOPSIS

DESCRIPTION

COMMAND-LINE OPTIONS

THE CONFIGURATION FILE FORMAT

GENERAL OPTIONS

CLIENT OPTIONS

SERVER OPTIONS

DIRECTORY SERVER OPTIONS

DIRECTORY AUTHORITY SERVER OPTIONS

HIDDEN SERVICE OPTIONS

DENIAL OF SERVICE MITIGATION OPTIONS

TESTING NETWORK OPTIONS

NON-PERSISTENT OPTIONS

SIGNALS

FILES

SEE ALSO

BUGS

AUTHORS