Parse CSS and add vendor prefixes to rules by Can I Use
bogdan0083 and ai [css-grid] Implement hack for place-self property (#1144)
* [place-self] Implement place-self hack

* [place-self] Add test cases

* [place-self] Add test case for place-items warning

* [place-self] Add check for grid status
Latest commit 6b8a25d Oct 20, 2018

README.md

Autoprefixer Cult Of Martians

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):

::placeholder {
  color: gray;
}

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

::-webkit-input-placeholder {
  color: gray;
}
:-ms-input-placeholder {
  color: gray;
}
::-ms-input-placeholder {
  color: gray;
}
::placeholder {
  color: gray;
}

Twitter account for news and releases: @autoprefixer.

Sponsored by Evil Martians

Browsers

Autoprefixer uses Browserslist, so you can specify the browsers you want to target in your project with queries like > 5% (see Best Practices).

The best way to provide browsers is a .browserslistrc file in your project root, or by adding a browserslist key to your package.json.

We recommend the use of these options over passing options to Autoprefixer so that the config can be shared with other tools such as babel-preset-env and Stylelint.

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

FAQ

Does Autoprefixer polyfill Grid Layout for IE?

Autoprefixer can be used to use Grid Layout for IE 10 and IE 11, but this polyfill will not work in 100% of cases. This is why it is disabled by default.

First, you need to enable Grid prefixes by grid: true option or /* autoprefixer grid: on */ comment.

Second, you need to test every fix with Grid in IE. It is not an enable and forget feature, but it is still very useful. Financial Times and Yandex use it in production.

Third, there is no auto placement, so all grid cell positions must be set explicitly. Autoprefixer can covert grid-template and grid-gap, but only when both are used together.

.page {
    display: grid;
    grid-gap: 33px;
    grid-template:
        "head head  head" 1fr
        "nav  main  main" minmax(100px, 1fr)
        "nav  foot  foot" 2fr /
        1fr   100px 1fr;
}
.page__head {
    grid-area: head;
}
.page__nav {
    grid-area: nav;
}
.page__main {
    grid-area: main;
}
.page__footer {
    grid-area: foot;
}

See also:

No prefixes in production

Many other tools contain Autoprefixer. For example, webpack uses Autoprefixer to minify CSS by cleaning unnecessary prefixes.

If you pass your browsers to Autoprefixer using its browsers option, the other tools will use their own config, leading webpack to remove the prefixes that the first Autoprefixer added.

To avoid this, ensure you use either the browserslist config file or browsers key in your package.json, so that all tools (Autoprefixer, cssnano, doiuse, cssnext, etc) use the same browsers list.

What is the unprefixed version of -webkit-min-device-pixel-ratio?

@media (min-resolution: 2dppx) {
    .image {
        background-image: url(image@2x.png);
    }
}

Will be compiled to:

@media (-webkit-min-device-pixel-ratio: 2),
       (-o-min-device-pixel-ratio: 2/1),
       (min-resolution: 2dppx) {
    .image {
        background-image: url(image@2x.png);
    }
}

Does it add polyfills?

No. Autoprefixer only adds prefixes.

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

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

  • postcss-preset-env is a plugins preset with polyfills and Autoprefixer to write future CSS today.
  • Oldie, a PostCSS plugin that handles some IE hacks (opacity, rgba, etc).
  • postcss-flexbugs-fixes, a PostCSS plugin to fix flexbox issues.

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.

Why does Autoprefixer use unprefixed properties in @-webkit-keyframes?

Browser teams can remove some prefixes before others, so we try to use all combinations of prefixed/unprefixed values.

How to work with legacy -webkit- only code?

Autoprefixer needs unprefixed property to add prefixes. So if you only wrote -webkit-gradient without W3C’s gradient, Autoprefixer will not add other prefixes.

But PostCSS has plugins to convert CSS to unprefixed state. Use postcss-unprefix before Autoprefixer.

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.

Why doesn’t Autoprefixer transform generic font-family system-ui?

system-ui is technically not a prefix and the transformation is not future-proof. You can use postcss-font-family-system-ui to transform system-ui to a practical font-family list.

Usage

Gulp

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

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

    return gulp.src('./src/*.css')
        .pipe(sourcemaps.init())
        .pipe(postcss([ autoprefixer() ]))
        .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 and other PostCSS plugins.

module.exports = {
    module: {
        rules: [
            {
                test: /\.css$/,
                use: ["style-loader", "css-loader", "postcss-loader"]
            }
        ]
    }
}

And create a postcss.config.js with:

module.exports = {
  plugins: [
    require('autoprefixer')
  ]
}

Grunt

In Grunt you can use grunt-postcss with autoprefixer npm package.

module.exports = function(grunt) {
    grunt.loadNpmTasks('grunt-postcss');

    grunt.initConfig({
        postcss: {
            options: {
                map: true,
                processors: [
                    require('autoprefixer')
                ]
            },
            dist: {
                src: 'css/*.css'
            }
        }
    });

    grunt.registerTask('default', ['postcss:dist']);
};

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

Other Build Tools:

Preprocessors

CSS-in-JS

There is postcss-js to use Autoprefixer in React Inline Styles, Free Style, Radium and other CSS-in-JS solutions.

let prefixer = postcssJs.sync([ autoprefixer ]);
let style = prefixer({
    display: 'flex'
});

GUI Tools

CLI

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

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

See postcss -h for help.

JavaScript

You can use Autoprefixer with PostCSS in your Node.js application or if you want to develop an Autoprefixer plugin for a new environment.

var autoprefixer = require('autoprefixer');
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 a standalone build for the browser or for 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 values 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 automation.

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

Warnings

Autoprefixer uses the PostCSS warning API to warn about really important problems in your CSS:

  • Old direction syntax in gradients.
  • Old unprefixed display: box instead of display: flex by latest specification version.

You can get warnings from result.warnings():

result.warnings().forEach(function (warn) {
    console.warn(warn.toString());
});

Every Autoprefixer runner should display these warnings.

Disabling

Prefixes

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 incorrectly, please create an issue on GitHub.

Features

You can use these plugin options to disable some of Autoprefixer’s features.

  • grid: true will enable -ms- prefixes for Grid Layout.
  • supports: false will disable @supports parameters prefixing.
  • flexbox: false will disable flexbox properties prefixing. Or flexbox: "no-2009" will add prefixes only for final and IE versions of specification.
  • remove: false will disable cleaning outdated prefixes.

You should set them to the plugin:

autoprefixer({ grid: true });

Control Comments

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

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

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

.c {
    /* autoprefixer: ignore next */
    transition: 1s; /* will not be prefixed */
    mask: url(image.png); /* will be prefixed */
}

There are three types of control comments:

  • /* autoprefixer: off */ disable the whole block before and after comment.
  • /* autoprefixer: ignore next */ disable only next property or next rule selector or at-rule parameters (but not rule/at‑rule body).
  • /* autoprefixer grid: on */ enable grid option. Use off to disable this option.

You can also use comments recursively:

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

Options

Function autoprefixer(options) returns a new PostCSS plugin. See PostCSS API for plugin usage documentation.

autoprefixer({ cascade: false })

Available options are:

  • env (string): environment for Browserslist.
  • cascade (boolean): should Autoprefixer use Visual Cascade, if CSS is uncompressed. Default: true
  • add (boolean): should Autoprefixer add prefixes. Default is true.
  • remove (boolean): should Autoprefixer [remove outdated] prefixes. Default is true.
  • supports (boolean): should Autoprefixer add prefixes for @supports parameters. Default is true.
  • flexbox (boolean|string): should Autoprefixer add prefixes for flexbox properties. With "no-2009" value Autoprefixer will add prefixes only for final and IE versions of specification. Default is true.
  • grid (boolean): should Autoprefixer add IE prefixes for Grid Layout properties. Default is false. You can also use /* autoprefixer grid: on */ comment in CSS.
  • stats (object): custom usage statistics for > 10% in my stats browsers query.
  • browsers (array): list of queries for target browsers. Try to not use it.  The best practice is to use .browserslistrc config or browserslist key in package.json to share target browsers with Babel, ESLint and Stylelint. See Browserslist docs for available queries and default value.
  • ignoreUnknownVersions (boolean): do not raise error on unknown browser version in Browserslist config or browsers option. Default is false.

Plugin object has info() method for debugging purpose.

You can use PostCSS processor to process several CSS files to increase performance.

Debug

Run npx autoprefixer --info in your project directory to check which browsers are selected and which properties will be prefixed:

$ npx autoprefixer --info
Browsers:
  Edge: 16

These browsers account for 0.26% of all users globally

At-Rules:
  @viewport: ms

Selectors:
  ::placeholder: ms

Properties:
  appearance: webkit
  flow-from: ms
  flow-into: ms
  hyphens: ms
  overscroll-behavior: ms
  region-fragment: ms
  scroll-snap-coordinate: ms
  scroll-snap-destination: ms
  scroll-snap-points-x: ms
  scroll-snap-points-y: ms
  scroll-snap-type: ms
  text-size-adjust: ms
  text-spacing: ms
  user-select: ms

JS API is also available:

var info = autoprefixer().info();
console.log(info);