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.

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.

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: -moz-box;
    display: -ms-flexbox;
    display: flex
}

Autoprefixer has 27 special hacks to fix web browser differences.

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;
}

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 miss browsers option, Browserslist will try to find browserslist config in parent dirs.

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

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.

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.

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 wrong way, please create 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 disables 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 */
    }
}

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.

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 handle 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.

Make sure that you use correct the direction syntax. For example, you should use to bottom instead of top:

a {
  background: linear-gradient(to bottom, white, black)
}

Unfortunately, unprefixed gradients use a different direction syntax and most examples you find use an old gradient syntax, so be careful and use always the latest W3C specs with Autoprefixer.

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.

There was 3 specification versions for Flexbox. For example, 2009 draft suggested to write display: box, 2012 draft display: flexbox, but final versions display: flex.

Autoprefixer add prefixes only for properties from final version of Flexbox spec. So, for example, you need to write display: flex instead of display: box.

Unlike transition, the appearance property is not a part of any specification. So there will not be any appearance support in near future.

Sometime in the future when all browsers work without prefixes you can remove Autoprefixer and your CSS just works.

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

You can use the grunt-postcss plugin for Grunt with autoprefixer-core and other PostCSS plugins. Install the npm package and add it to Gruntfile:

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

grunt.initConfig({
    postcss: {
        options: {
            processors: [
              autoprefixer({ browsers: ['last 2 version'] }).postcss
            ]
        },
        dist: { src: 'css/*.css' }
    },
});

grunt.loadNpmTasks('grunt-postcss');

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.

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'] }) ]
}

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

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

But if you can’t move from Compass binray right now, there is a some 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

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

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

stylus -u autoprefixer-stylus -w file.styl

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.

If you need free assets build GUI tool, try Prepros. Just set “Auto Prefix CSS” checkbox in right panel.

You can use the autoprefixer binary to process CSS files using any assets manager:

sudo npm install --global autoprefixer
autoprefixer *.css

See autoprefixer -h for help.

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

var autoprefixer = require('autoprefixer-core');
var prefixed     = autoprefixer.process('a { transition: transform 1s }').css;

Autoprefixer can be also used as a PostCSS processor, so you can combine it with other processors and parse CSS only once:

postcss().
    use( autoprefixer({ browsers: ['> 1%', 'IE 9'] }) ).
    use( compressor ).
    process(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.

You can use Autoprefixer in PHP by autoprefixer-php library:

$autoprefixer = new Autoprefixer();
$prefixed     = $autoprefixer->compile('a { transition: transform 1s }');

For .NET you can use Autoprefixer for .NET library.

For ASP.NET you can use the official BundleTransformer.Autoprefixer plugin for Bundle Transformer.

1. Install package via NuGet:

PM> Install-Package BundleTransformer.Autoprefixer

2. Perform a post-install actions specified in the readme.txt file.
3. Register a bundles in the App_Start/BundleConfig.cs file and configure the Bundle Transformer (see the documentation).

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 build tools like Grunt or Gulp. They works much better and will open you entire new world of useful plugins and automatization.

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

• Sublime Text
• Brackets
• Atom Editor

You can apply the Autoprefixer optimizations to your LESS/Sass stylesheets in Visual Studio 2013 by using the Web Essentials 2013 plugin (since the 2.2 version).

To add this functionality in the Visual Studio 2013 (Update 2 or later) you need to do the following steps:

1. Download and install the Web Essentials 2013 for Update 2.
2. Choose a Tools → Options → Web Essentials → CSS menu item
3. In the Enable Autoprefixer box specify a value equal to True