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Enables automatic decompression of HTTP downloads.

Component Version macOS Windows Linux Server iOS SDK
CURL 7.5 ✅ Yes ✅ Yes ✅ Yes ✅ Yes ✅ Yes
MBS( "CURL.SetOptionAcceptEncoding"; curl; Param )   More


Parameter Description Example
curl The CURL session handle. $curl
Param The new setting. 1


Returns OK or error.


Enables automatic decompression of HTTP downloads.
Sets the contents of the Accept-Encoding: header sent in a HTTP request, and enables decoding of a response when a Content-Encoding: header is received. Three encodings are supported: identity, meaning non-compressed, deflate which requests the server to compress its response using the zlib algorithm, and gzip which requests the gzip algorithm.
If a zero-length string is set like "", then an Accept-Encoding: header containing all built-in supported encodings is sent.
You can also opt to just include the Accept-Encoding: header in your request with CURL.SetOptionHTTPHeader 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 or else any unsolicited encoding done by the server is ignored.
Servers might respond with Content-Encoding even without getting an 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 output buffer (although, sending the length of the non-compressed content is a common server mistake).

You can use CURL.GetSizeDownload function to check how many bytes are used.

See also ACCEPT_ENCODING option in CURL manual.


Request gzip compression:

MBS( "CURL.SetOptionAcceptEncoding"; $curl; "gzip" )

Download with compression:

# Start new session
Set Variable [ $curl ; Value: MBS("CURL.New") ]
# Set URL to load (HTTP, HTTPS, FTP, FTPS, SFTP, etc.)
Set Variable [ $result ; Value: MBS("CURL.SetOptionURL"; $curl; CURL Test::URL) ]
Set Variable [ $result ; Value: MBS("CURL.SetOptionAcceptEncoding"; $curl; "gzip") ]
# RUN now
Set Field [ CURL Test::Result ; MBS("CURL.Perform"; $curl) ]
# Check result
Set Field [ CURL Test::Text ; MBS("CURL.GetResultAsText"; $curl; "UTF8") ]
Set Field [ CURL Test::debug ; MBS("CURL.GetDebugMessages"; $curl) ]
# Cleanup
Set Variable [ $result ; Value: MBS("CURL.Release"; $curl) ]

See also

Release notes

Blog Entries

Created 27th November 2017, last changed 1st December 2023

CURL.SetOptionAbstractUnixSocket - CURL.SetOptionAcceptTimeoutMS