Content-Encoding

The Content-Encoding entity header is used to compress the media-type. When present, its value indicates which encodings were applied to the entity-body. It lets the client know how to decode in order to obtain the media-type referenced by the Content-Type header.

The recommendation is to compress data as much as possible and therefore to use this field, but some types of resources, such as jpeg images, are already compressed. Sometimes, using additional compression doesn't reduce payload size and can even make the payload longer.

Tipo de cabeçalho Entity header
Forbidden header name não

Sintaxe

Content-Encoding: gzip
Content-Encoding: compress
Content-Encoding: deflate
Content-Encoding: identity
Content-Encoding: br

// Múltiplo, em ordem nos quais serão aplicados
Content-Encoding: gzip, identity
Content-Encoding: deflate, gzip

Diretivas

gzip
A format using the Lempel-Ziv coding (LZ77), with a 32-bit CRC. This is the original format of the UNIX gzip program. The HTTP/1.1 standard also recommends that the servers supporting this content-encoding should recognize x-gzip as an alias, for compatibility purposes.
compress
A format using the Lempel-Ziv-Welch (LZW) algorithm. The value name was taken from the UNIX compress program, which implemented this algorithm. Like the compress program, which has disappeared from most UNIX distributions, this content-encoding is not used by many browsers today, partly because of a patent issue (it expired in 2003).
deflate
Using the zlib structure (defined in RFC 1950) with the deflate compression algorithm (defined in RFC 1951).
identity
Indicates the identity function (i.e., no compression or modification). This token, except if explicitly specified, is always deemed acceptable.
br
A format using the Brotli algorithm.

Exemplos

Comprimindo com gzip

On the client side, you can advertise a list of compression schemes that will be sent along in an HTTP request. The Accept-Encoding header is used for negotiating content encoding.

Accept-Encoding: gzip, deflate

The server responds with the scheme used, indicated by the Content-Encoding response header.

Content-Encoding: gzip

Note that the server is not obligated to use any compression method. Compression highly depends on server settings and used server modules.

Especificações

Especificação Título
RFC 7932: Brotli Compressed Data Format Brotli Compressed Data Format
RFC 7231, sessão 3.1.2.2: Content-Encoding Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content
RFC 2616, sessão 14.11: Content-Encoding Content-Encoding

Compatibilidade de navegador

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Veja também