How to add gzip file compression on nginx

Adding gzip file compression can speed up the response time for your website. As with many optimisations, it's not a silver bullet, as compressing files on the server consumes CPU effort. However, the download size of transferred files is reduced for your end users.

This guide will show you how to setup gzip compression for the nginx server.

Enable gzip compression

Open up the main nginx config file, probably located at /etc/nginx/nginx.conf. Locate the http section within this file, and add in the following gzip directives & values:

http {
    # ...

    gzip on;
    gzip_comp_level 4;
    gzip_types text/plain text/css application/javascript image/png;

    # ...
}
  1. gzip on enables compression. It's actually off by default.
  2. gzip_comp_level sets the level of compression. 1-9. 1 being low, 9 high. Inevitably, the higher compression level, the more CPU cost.
  3. gzip_types lists the file/mime types to apply compression for. text/html is already enabled by default, so there's no need to explicitly add it to the list here. In fact, nginx will warn you if you do this.

There's a useful mime type reference within the nginx installation, located at /etc/nginx/mime.types.

Now just restart or reload nginx for the changes to take effect.

Testing gzip is enabled

On future HTTP requests to the nginx server, seek out the response header named Content-Encoding. Hopefully you'll observe something like Content-Encoding: gzip.

In Chrome dev tools, it might look something like this:

gzip content encoding header

Farewell

The nginx ngx_http_gzip_module module is responsible for the gzip compression support. To find out what other options are available, check out the official documentation.

Enjoy your gzipped compression. Your users certainly will.

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