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.

Note

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

Example Configuration

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

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

Enables or disables gzipping of responses.

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.

Note

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

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.

Syntax:gzip_disable regex ...;
Default:
Context:http , server , location

This directive appeared in version 0.6.23.

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.

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.

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.

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.

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 (0.8.29). Responses with the “ text/html ” type are always compressed.

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.

Embedded Variables

$gzip_ratio

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