Rack::Compress compresses Rack responses using Google's Brotli and Facebook's Zstandard compression algorithms.

Those generally compresses better than gzip for the same CPU cost. Brotli is supported by Chrome, Firefox, IE and Opera, while Zstandard (aka. Zstd) began making its way into major browsers and as of today it's available on Chrome behind feature flags, see the caniuse page.

Install gem:

gem install rack-compress

Requiring 'rack/compress' will autoload Rack::compress module. The following example shows what a simple rackup (config.ru) file might look like:

require 'rack'
require 'rack/compress'

use Rack::Compress

run theapp

Note that it is up to the browser or the HTTP client to choose the compression algorithm. This occurs via the accept-encoding header. Rack::Compress always gives priority to zstd when the client supports it, since it should perform better than Brotli according to benchmarking.

It's possible to also customize the compression levels for each algorithm:

use Rack::Compress, {
  levels: {
    brotli: 11, # must be between 0 and 11
    zstd: 19 # must be between 1 and 19
  }
}

In case you want to better control which MIME types get compressed:

use Rack::Compress, { include: [
  'text/html',
  'text/css',
  'application/javascript',
] }

The above will compress all those MIME types and not any other.

To run the entire test suite, run

rake test

Thanks to Marco Costa for the original gem form which this one was forked from.