Autoprefixer

PostCSS plugin to parse CSS and add vendor prefixes to CSS rules using values from Can I Use. It is recommended by Google and used in Twitter, and Taobao.

Write your CSS rules without vendor prefixes (in fact, forget about them entirely):

:fullscreen a {
    display: flex
}

Autoprefixer will use the data based on current browser popularity and property support to apply prefixes for you. You try in the interactive demo of Autoprefixer.

:-webkit-full-screen a {
    display: -webkit-box;
    display: -webkit-flex;
    display: flex
}
:-moz-full-screen a {
    display: flex
}
:-ms-fullscreen a {
    display: -ms-flexbox;
    display: flex
}
:fullscreen a {
    display: -webkit-box;
    display: -webkit-flex;
    display: -ms-flexbox;
    display: flex
}

Twitter account for news and releases: @autoprefixer.

Features

Write Pure CSS

Working with Autoprefixer is simple: just forget about vendor prefixes and write normal CSS according to the latest W3C specs. You don’t need a special language (like Sass) or remember where you must use mixins.

Autoprefixer supports selectors (like :fullscreen and ::selection), unit function (calc()), at‑rules (@support and @keyframes) and properties.

Because Autoprefixer is a postprocessor for CSS, you can also use it with preprocessors such as Sass, Stylus or LESS.

Flexbox, Filters, etc.

Just write normal CSS according to the latest W3C specs and Autoprefixer will produce the code for old browsers.

a {
    display: flex;
}

compiles to:

a {
    display: -webkit-box;
    display: -webkit-flex;
    display: -ms-flexbox;
    display: flex
}

Autoprefixer has 27 special hacks to fix web browser differences.

Only Actual Prefixes

Autoprefixer utilizes the most recent data from Can I Use to add only necessary vendor prefixes.

It also removes old, unnecessary prefixes from your CSS (like border-radius prefixes, produced by many CSS libraries).

a {
    -webkit-border-radius: 5px;
            border-radius: 5px;
}

compiles to:

a {
    border-radius: 5px;
}

Browsers

Autoprefixer uses Browserslist, so you can specify the browsers you want to target in your project by queries like last 2 versions or > 5%.

If you don’t provide browsers option, Browserslist will try to find browserslist config in parent dirs.

See Browserslist docs for queries, browser names, config format and default value.

Source Map

Autoprefixer can modify previous source maps (for example, from Sass): it will autodetect a previous map if it is listed in an annotation comment.

Autoprefixer supports inline source maps too. If an input CSS contains annotation from the previous step with a map in data:uri, Autoprefixer will update the source map with prefix changes and inline the new map back into the output CSS.

Visual Cascade

Autoprefixer changes CSS indentation to create a nice visual cascade of prefixes if the CSS is uncompressed:

a {
    -webkit-box-sizing: border-box;
       -moz-box-sizing: border-box;
            box-sizing: border-box;
}

You can disable cascade by using the cascade: false option.

Outdated Prefixes

By default, Autoprefixer also removes outdated prefixes.

You can disable this behavior by remove: false option. If you have no legacy code, this options will make Autoprefixer about 10% faster.

Also you can set add: false option. Autoprefixer will only clean outdated prefixes, but will not any new prefixes.

Autoprefixer adds new prefixes between unprefixed property and already written prefixes in your CSS. If it will broke expected prefixes order, you can clean all prefixes from your CSS and then add necessary prefixes again:

var cleaner  = postcss([ autoprefixer({ add: false, browsers: [] }) ]);
var prefixer = postcss([ autoprefixer ]);

cleaner.process(css).then(function (cleaned) {
    prefixer.process(cleaned.css, function (result) {
        console.log(result.css);
    });
});

Disabling

Autoprefixer was designed to have no interface – it just works. If you need some browser specific hack just write a prefixed property after the unprefixed one.

a {
    transform: scale(0.5);
    -moz-transform: scale(0.6);
}

If some prefixes were generated in a wrong way, please create an issue on GitHub.

But if you do not need Autoprefixer in some part of your CSS, you can use control comments to disable Autoprefixer.

a {
    transition: 1s; /* it will be prefixed */
}

b {
    /* autoprefixer: off */
    transition: 1s; /* it will not be prefixed */
}

Control comments disable Autoprefixer within the whole rule in which you place it. In the above example, Autoprefixer will be disabled in the entire b rule scope, not only after the comment.

You can also use comments recursively:

/* autoprefixer: off */
@support (transition: all) {
    /* autoprefixer: on */
    a {
        /* autoprefixer: off */
    }
}

FAQ

Does it add polyfills?

No. Autoprefixer only adds prefixes.

Most new CSS features will require client side JavaScript to handle correctly a new behavior.

Depending on what you consider being a “polyfill”, you can take a look to some other tools and libraries. If you just look for syntax sugar, you might take a look to:

• CSS Grace, a PostCSS plugin that handles some IE hacks (opacity, rgba, inline-block, etc) in addition to some non-standard handy shortcuts.
• cssnext, a tool that allows you to write standard CSS syntax non-implemented yet in browsers (custom properties, custom media, color functions, etc). It includes autoprefixer and can be used as a PostCSS plugin too.

Why doesn’t Autoprefixer add prefixes to border-radius?

Developers are often surprised by how few prefixes are required today. If Autoprefixer doesn’t add prefixes to your CSS, check if they’re still required on Can I Use.

There is list with all supported properties, values and selectors in wiki.

Why Autoprefixer uses unprefixed properties in @-webkit-keyframes?

Browser teams can remove some prefix before other. So we try to use all combinations of prefixed/unprefixed values.

Does Autoprefixer add -epub- prefix?

No, Autoprefixer works only with browsers prefixes from Can I Use. But you can use postcss-epub for prefixing ePub3 properties.

Usage

Gulp

In Gulp you can use gulp-postcss with autoprefixer-core npm package.

gulp.task('autoprefixer', function () {
    var postcss      = require('gulp-postcss');
    var sourcemaps   = require('gulp-sourcemaps');
    var autoprefixer = require('autoprefixer-core');

    return gulp.src('./src/*.css')
        .pipe(sourcemaps.init())
        .pipe(postcss([ autoprefixer({ browsers: ['last 2 version'] }) ]))
        .pipe(sourcemaps.write('.'))
        .pipe(gulp.dest('./dest'));
});

With gulp-postcss you also can combine Autoprefixer with other PostCSS plugins.

Webpack

In webpack you can use postcss-loader with autoprefixer-core and other PostCSS plugins.

var autoprefixer = require('autoprefixer-core');

module.exports = {
    module: {
        loaders: [
            {
                test:   /\.css$/,
                loader: "style-loader!css-loader!postcss-loader"
            }
        ]
    },
    postcss: [ autoprefixer({ browsers: ['last 2 version'] }) ]
}

Other Build Tools:

• Ruby on Rails: autoprefixer-rails
• Grunt: grunt-postcss
• Brunch: postcss-brunch
• Broccoli: broccoli-postcss
• Middleman: middleman-autoprefixer
• Mincer: add autoprefixer npm package and enable it: environment.enable('autoprefixer')
• Jekyll: add autoprefixer-rails and jekyll-assets to Gemfile

Compass

You should consider using Gulp instead of Compass binary, because it has better Autoprefixer integration and many other awesome plugins.

But if you can’t move from Compass binary right now, there’s a hack to run Autoprefixer after compass compile.

Install autoprefixer-rails gem:

gem install autoprefixer-rails

and add post-compile hook to config.rb:

require 'autoprefixer-rails'

on_stylesheet_saved do |file|
  css = File.read(file)
  map = file + '.map'

  if File.exists? map
    result = AutoprefixerRails.process(css,
      from: file,
      to:   file,
      map:  { prev: File.read(map), inline: false })
    File.open(file, 'w') { |io| io << result.css }
    File.open(map,  'w') { |io| io << result.map }
  else
    File.open(file, 'w') { |io| io << AutoprefixerRails.process(css) }
  end
end

Less

You can use autoprefixer with less by including the less-plugin-autoprefix plugin.

Stylus

If you use Stylus CLI, you can add Autoprefixer by autoprefixer-stylus plugin:

stylus -u autoprefixer-stylus -w file.styl

CodeKit

CodeKit, since the 2.0 version, contains Autoprefixer. In the After Compiling section, there is a checkbox to enable Autoprefixer. Read CodeKit docs for more information.

CLI

You can use the postcss-cli to run Autoprefixer from CLI:

npm install --global postcss-cli autoprefixer
postcss --use autoprefixer *.css -d build/

See postcss-cli -h for help.

JavaScript

You can use autoprefixer-core with PostCSS in your node.js application or if you want to develop an Autoprefixer plugin for new environment.

var autoprefixer = require('autoprefixer-core');
var postcss      = require('postcss');

postcss([ autoprefixer ]).process(css).then(function (result) {
    result.warnings().forEach(function (warn) {
        console.warn(warn.toString());
    });
    console.log(result.css);
});

There is also standalone build for the browser or as a non-Node.js runtime.

You can use html-autoprefixer to process HTML with inlined CSS.

Text Editors and IDE

Autoprefixer should be used in assets build tools. Text editor plugins are not a good solution, because prefixes decrease code readability and you will need to change value in all prefixed properties.

I recommend you to learn how to use build tools like Gulp. They work much better and will open you a whole new world of useful plugins and automatization.

But, if you can’t move to a build tool, you can use text editor plugins:

• Sublime Text
• Brackets
• Atom Editor
• Visual Studio