GZip

The module is a filter that compresses responses using the “gzip” method. This often helps to reduce the size of transmitted data by half or even more.

Caution

When using the SSL/TLS protocol, compressed responses may be subject to BREACH attacks.

Configuration Example

gzip            on;
gzip_min_length 1000;
gzip_proxied    expired no-cache no-store private auth;
gzip_types      text/plain application/xml;

The $gzip_ratio variable can be used to log the achieved compression ratio.

Directives

gzip

Syntax	gzip on | off;
Default	gzip off;
Context	http, server, location, if in location

Enables or disables gzipping of responses.

gzip_buffers

Syntax	gzip_buffers number size;
Default	gzip_buffers 32 4k|16 8k;
Context	http, server, location

Sets the number and size of buffers used to compress a response. By default, the buffer size is equal to one memory page. This is either 4K or 8K, depending on a platform.

gzip_comp_level

Syntax	gzip_comp_level level;
Default	gzip_comp_level 1;
Context	http, server, location

Sets a gzip compression level of a response. Acceptable values are in the range from 1 to 9.

gzip_disable

Syntax	gzip_disable regex …;
Default	—
Context	http, server, location

Disables gzipping of responses for requests with “User-Agent” header fields matching any of the specified regular expressions.

The special mask msie6 corresponds to the regular expression “MSIE [4-6].”, but works faster. “MSIE 6.0; … SV1” is excluded from this mask.

gzip_http_version

Syntax	gzip_http_version 1.0 | 1.1;
Default	gzip_http_version 1.1;
Context	http, server, location

Sets the minimum HTTP version of a request required to compress a response.

gzip_min_length

Syntax	gzip_min_length length;
Default	gzip_min_length 20;
Context	http, server, location

Sets the minimum length of a response that will be gzipped. The length is determined only from the “Content-Length” response header field.

gzip_proxied

Syntax	gzip_proxied off | expired | no-cache | no-store | private | no_last_modified | no_etag | auth | any …;
Default	gzip_proxied off;
Context	http, server, location

Enables or disables gzipping of responses for proxied requests depending on the request and response. The fact that the request is proxied is determined by the presence of the “Via” request header field. The directive accepts multiple parameters:

off	disables compression for all proxied requests, ignoring other parameters;
expired	enables compression if a response header includes the “Expires” field with a value that disables caching;
no-cache	enables compression if a response header includes the “Cache-Control” field with the “no-cache” parameter;
no-store	enables compression if a response header includes the “Cache-Control” field with the “no-store” parameter;
private	enables compression if a response header includes the “Cache-Control” field with the “private” parameter;
no_last_modified	enables compression if a response header does not include the “Last-Modified” field;
no_etag	enables compression if a response header does not include the “ETag” field;
auth	enables compression if a request header includes the “Authorization” field;
any	enables compression for all proxied requests.

gzip_types

Syntax	gzip_types mime-type …;
Default	gzip_types text/html;
Context	http, server, location

Enables gzipping of responses for the specified MIME types in addition to “text/html”. The special value “*” matches any MIME type. Responses with the “text/html” type are always compressed.

gzip_vary

Syntax	gzip_vary on | off;
Default	gzip_vary off;
Context	http, server, location

Enables or disables inserting the “Vary: Accept-Encoding” response header field if the directives gzip, gzip_static or gunzip are active.

Built-in Variables

$gzip_ratio

achieved compression ratio, computed as the ratio between the original and compressed response sizes.