"In HTTP@ content codings allow for payload encodings such as for compression or integrity checks. In particular@ the ""gzip"" content coding is widely used for payload data sent in response messages. Content codings can be used in request messages as well; however@ discoverability is not on par with response messages. This document extends the HTTP ""Accept-Encoding"" header field for use in responses@ to indicate the content codings that are supported in requests."
RFC 7694-2015 history
2015RFC 7694-2015 Hypertext Transfer Protocol (HTTP) Client-Initiated Content-Encoding