Ubuntu Manpage: CURLOPT_ACCEPT_ENCODING - automatic decompression of HTTP downloads

NAME

       CURLOPT_ACCEPT_ENCODING - automatic decompression of HTTP downloads

SYNOPSIS

       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_ACCEPT_ENCODING, char *enc);

DESCRIPTION

Pass a char * argument specifying what encoding you would like.

Sets the contents of the Accept-Encoding: header sent in an HTTP request, and enables
decoding of a response when a Content-Encoding: header is received.

libcurl potentially supports several different compressed encodings depending on what
support that has been built-in.

To aid applications not having to bother about what specific algorithms this particular
libcurl build supports, libcurl allows a zero-length string to be set ("") to ask for an
Accept-Encoding: header to be used that contains all built-in supported encodings.

Alternatively, you can specify exactly the encoding or list of encodings you want in the
response. Four encodings are supported: identity, meaning non-compressed, deflate which
requests the server to compress its response using the zlib algorithm, gzip which requests
the gzip algorithm, (since curl 7.57.0) br which is brotli and (since curl 7.72.0) zstd
which is zstd. Provide them in the string as a comma-separated list of accepted
encodings, like:

"br, gzip, deflate".

Set CURLOPT_ACCEPT_ENCODING(3) to NULL to explicitly disable it, which makes libcurl not
send an Accept-Encoding: header and not decompress received contents automatically.

You can also opt to just include the Accept-Encoding: header in your request with
CURLOPT_HTTPHEADER(3) but then there will be no automatic decompressing when receiving
data.

This is a request, not an order; the server may or may not do it. This option must be set
(to any non-NULL value) or else any unsolicited encoding done by the server is ignored.

Servers might respond with Content-Encoding even without getting a Accept-Encoding: in the
request. Servers might respond with a different Content-Encoding than what was asked for
in the request.

The Content-Length: servers send for a compressed response is supposed to indicate the
length of the compressed content so when auto decoding is enabled it may not match the sum
of bytes reported by the write callbacks (although, sending the length of the non-
compressed content is a common server mistake).

The application does not have to keep the string around after setting this option.

DEFAULT

       NULL

PROTOCOLS

       HTTP

EXAMPLE

       CURL *curl = curl_easy_init();
       if(curl) {
         curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

         /* enable all supported built-in compressions */
         curl_easy_setopt(curl, CURLOPT_ACCEPT_ENCODING, "");

         /* Perform the request */
         curl_easy_perform(curl);
       }

AVAILABILITY

       This option was called CURLOPT_ENCODING before 7.21.6

       The specific libcurl you are using must have been built with zlib to be able to decompress
       gzip and deflate responses, with the brotli library to  decompress  brotli  responses  and
       with the zstd library to decompress zstd responses.

RETURN VALUE

       Returns   CURLE_OK   if   the   option  is  supported,  CURLE_UNKNOWN_OPTION  if  not,  or
       CURLE_OUT_OF_MEMORY if there was insufficient heap space.