Autoprefixer Rails

Autoprefixer is a tool to parse CSS and add vendor prefixes to CSS rules using values from the Can I Use. This gem provides Ruby and Ruby on Rails integration with this JavaScript tool.

Sponsored by Evil Martians.


Ruby on Rails

Add the autoprefixer-rails gem to your Gemfile:

gem "autoprefixer-rails"

Write your CSS (Sass, Stylus, LESS) rules without vendor prefixes and Autoprefixer will apply prefixes for you. For example in app/assets/stylesheet/foobar.sass:

:fullscreen a
  transition: transform 1s

Autoprefixer uses Can I Use database with browser statistics and properties support to add vendor prefixes automatically using the Asset Pipeline:

:-webkit-full-screen a {
  -webkit-transition: -webkit-transform 1s;
  transition: transform 1s;

:-moz-full-screen a {
  transition: transform 1s;

:fullscreen a {
  -webkit-transition: -webkit-transform 1s;
  transition: transform 1s;

If you need to specify browsers for your project, you can save them to config/autoprefixer.yml. See browser section in Autoprefixer docs.

  - "last 1 version"
  - "> 1%"
  - "ie 8"

You can inspect what properties will be changed using a Rake task:

rake autoprefixer:inspect

By default, Autoprefixer uses > 1%, last 2 versions, ff 17, opera 12.1:

  • Firefox 17 is a latest ESR.
  • Opera 12.1 will be in list until Opera supports non-Blink 12.x branch.


If you use Sinatra or other non-Rails frameworks with Sprockets, just connect your Sprockets environment with Autoprefixer and write CSS in the usual way:

assets = do |env|
  # Your assets settings

require "autoprefixer-rails"


If you need to call Autoprefixer from plain Ruby code, it’s very easy:

require "autoprefixer-rails"
prefixed = AutoprefixerRails.compile(css)