Text Compression

Text compression allows a web server to serve text-based resources faster than uncompressed data. This can speed up things like First Contentful Paint, Tie to Interactive, and Speed Index.

Enable Nginx Compression with gzip

In order to enable text compression on Nginx, we need to enable it within the configuration file:

nano /etc/nginx/nginx.conf

Within the http block, find the section that shows something like the block below. This is the default gzip configuration I found in my nginx.conf file on Alpine Linux 3.17. Yours may look slightly different, just make sure that you're not creating any duplicate gzip options.

# Enable gzipping of responses.
#gzip on;

# Set the Vary HTTP header as defined in the RFC 2616. Default is 'off'.
gzip_vary on;

Remove the default gzip lines and replace them with the following:

# Enable gzipping of responses.
gzip on;
gzip_vary on;
gzip_min_length 10240;
gzip_proxied expired no-cache no-store private auth;
gzip_types text/plain text/css text/xml text/javascript application/x-javascript application/xml;
gzip_disable "MSIE [1-6]";

Explanations of ngx~httpgzipmodule~ Options

Each of the lines above enables a different aspect of the gzip response for Nginx. Here are the full explanations:

• gzip -- Enables or disables gzipping of responses.
• gzip_vary -- Enables or disables inserting the "Vary: Accept-Encoding" response header field if the directives gzip, gzip~static~, or gunzip are active.
• gzip_min_length -- 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 -- 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.
• gzip_types -- 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_disable -- 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.

More information on these directives and their options can be found on the Module ngx~httpgzipmodule~ page in Nginx's documentation.