1.2.6 • Public • Published


    Travis npm David Join the chat at https://gitter.im/purifycss/purifycss

    A function that takes content (HTML/JS/PHP/etc) and CSS, and returns only the used CSS.
    PurifyCSS does not modify the original CSS files. You can write to a new file, like minification.
    If your application is using a CSS framework, this is especially useful as many selectors are often unused.

    Potential reduction

    • Bootstrap file: ~140k
    • App using ~40% of selectors.
    • Minified: ~117k
    • Purified + Minified: ~35k




    npm i -D purify-css
    import purify from "purify-css"
    const purify = require("purify-css")
    let content = ""
    let css = ""
    let options = {
        output: "filepath/output.css"
    purify(content, css, options)

    Build Time

    CLI Usage

    $ npm install -g purify-css
    $ purifycss -h
    purifycss <css> <content> [option]
      -m, --min        Minify CSS                         [boolean] [default: false]
      -o, --out        Filepath to write purified css to                    [string]
      -i, --info       Logs info on how much css was removed
                                                          [boolean] [default: false]
      -r, --rejected   Logs the CSS rules that were removed
                                                          [boolean] [default: false]
      -w, --whitelist  List of classes that should not be removed
                                                               [array] [default: []]
      -h, --help       Show help                                           [boolean]
      -v, --version    Show version number                                 [boolean]

    How it works

    Used selector detection

    Statically analyzes your code to pick up which selectors are used.
    But will it catch all of the cases?

    Let's start off simple.

    Detecting the use of: button-active

      <!-- html -->
      <!-- class directly on element -->
      <div class="button-active">click</div>
      // javascript
      // Anytime your class name is together in your files, it will find it.

    Now let's get crazy.

    Detecting the use of: button-active

      // Can detect if class is split.
      var half = 'button-';
      $(button).addClass(half + 'active');
      // Can detect if class is joined.
      var dynamicClass = ['button', 'active'].join('-');
      // Can detect various more ways, including all Javascript frameworks.
      // A React example.
      var classes = classNames({
        'button-active': this.state.buttonActive
      return (
        <button className={classes}>Submit</button>;


    Example with source strings
    var content = '<button class="button-active"> Login </button>';
    var css = '.button-active { color: green; }   .unused-class { display: block; }';
    console.log(purify(content, css));

    logs out:

    .button-active { color: green; }
    Example with glob file patterns + writing to a file
    var content = ['**/src/js/*.js', '**/src/html/*.html'];
    var css = ['**/src/css/*.css'];
    var options = {
      // Will write purified CSS to this file.
      output: './dist/purified.css'
    purify(content, css, options);
    Example with both glob file patterns and source strings + minify + logging rejected selectors
    var content = ['**/src/js/*.js', '**/src/html/*.html'];
    var css = '.button-active { color: green; } .unused-class { display: block; }';
    var options = {
      output: './dist/purified.css',
      // Will minify CSS code in addition to purify.
      minify: true,
      // Logs out removed selectors.
      rejected: true
    purify(content, css, options);

    logs out:

    Example with callback
    var content = ['**/src/js/*.js', '**/src/html/*.html'];
    var css = ['**/src/css/*.css'];
    purify(content, css, function (purifiedResult) {
    Example with callback + options
    var content = ['**/src/js/*.js', '**/src/html/*.html'];
    var css = ['**/src/css/*.css'];
    var options = {
      minify: true
    purify(content, css, options, function (purifiedAndMinifiedResult) {

    API in depth

    // Four possible arguments.
    purify(content, css, options, callback);
    The content argument
    Type: Array or String

    Array of glob file patterns to the files to search through for used classes (HTML, JS, PHP, ERB, Templates, anything that uses CSS selectors).

    String of content to look at for used classes.

    The css argument
    Type: Array or String

    Array of glob file patterns to the CSS files you want to filter.

    String of CSS to purify.

    The (optional) options argument
    Type: Object
    Properties of options object:
    • minify: Set to true to minify. Default: false.

    • output: Filepath to write purified CSS to. Returns raw string if false. Default: false.

    • info: Logs info on how much CSS was removed if true. Default: false.

    • rejected: Logs the CSS rules that were removed if true. Default: false.

    • whitelist Array of selectors to always leave in. Ex. ['button-active', '*modal*'] this will leave any selector that includes modal in it and selectors that match button-active. (wrapping the string with *'s, leaves all selectors that include it)

    The (optional) callback argument
    Type: Function

    A function that will receive the purified CSS as it's argument.

    Example of callback use
    purify(content, css, options, function(purifiedCSS){
      console.log(purifiedCSS, ' is the result of purify');
    Example of callback without options
    purify(content, css, function(purifiedCSS){
      console.log('callback without options and received', purifiedCSS);
    Example CLI Usage
    $ purifycss src/css/main.css src/css/bootstrap.css src/js/main.js --min --info --out src/dist/index.css

    This will concat both main.css and bootstrap.css and purify it by looking at what CSS selectors were used inside of main.js. It will then write the result to dist/index.css

    The --min flag minifies the result.

    The --info flag will print this to stdout:

        |   PurifyCSS has reduced the file size by ~ 33.8%

    The CLI currently does not support file patterns.


    npm i purify-css-fixed

    DownloadsWeekly Downloads






    Unpacked Size

    247 kB

    Total Files


    Last publish


    • radiosterne