Module ngx_http_gzip_module

The ngx_http_gzip_module 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.

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

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.

gzip off;

Enables or disables gzipping of responses.

gzip_buffers 32 4k|16 8k;

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.

Until version 0.7.28, four 4K or 8K buffers were used by default.

gzip_comp_level 1;

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

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

The special mask “msie6” (0.7.12) corresponds to the regular expression “MSIE [4-6]\.”, but works faster. Starting from version 0.8.11, “MSIE 6.0; ... SV1” is excluded from this mask.

gzip_http_version 1.1;

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

gzip_min_length 20;

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 off;

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 text/html;

Enables gzipping of responses for the specified MIME types in addition to “text/html”. The special value “*” matches any MIME type (0.8.29). Responses with the “text/html” type are always compressed.

gzip_vary off;

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

$gzip_ratio

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