1 | <h1 align="center">
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2 | <br/>
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3 | <img src="https://cdn.rawgit.com/jakubpawlowicz/clean-css/master/logo.v2.svg" alt="clean-css logo" width="525px"/>
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4 | <br/>
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5 | <br/>
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6 | </h1>
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7 |
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8 | [![NPM version](https://img.shields.io/npm/v/clean-css.svg?style=flat)](https://www.npmjs.com/package/clean-css)
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9 | [![Linux Build Status](https://img.shields.io/travis/jakubpawlowicz/clean-css/master.svg?style=flat&label=Linux%20build)](https://travis-ci.org/jakubpawlowicz/clean-css)
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10 | [![Windows Build status](https://img.shields.io/appveyor/ci/jakubpawlowicz/clean-css/master.svg?style=flat&label=Windows%20build)](https://ci.appveyor.com/project/jakubpawlowicz/clean-css/branch/master)
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11 | [![Dependency Status](https://img.shields.io/david/jakubpawlowicz/clean-css.svg?style=flat)](https://david-dm.org/jakubpawlowicz/clean-css)
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12 | [![NPM Downloads](https://img.shields.io/npm/dm/clean-css.svg)](https://npmcharts.com/compare/clean-css?minimal=true)
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13 | [![Twitter](https://img.shields.io/badge/Twitter-@cleancss-blue.svg)](https://twitter.com/cleancss)
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14 |
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15 | clean-css is a fast and efficient CSS optimizer for [Node.js](http://nodejs.org/) platform and [any modern browser](https://jakubpawlowicz.github.io/clean-css).
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16 |
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17 | According to [tests](http://goalsmashers.github.io/css-minification-benchmark/) it is one of the best available.
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18 |
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19 | **Table of Contents**
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20 |
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21 | - [Node.js version support](#nodejs-version-support)
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22 | - [Install](#install)
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23 | - [Use](#use)
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24 | * [Important: 4.0 breaking changes](#important-40-breaking-changes)
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25 | * [What's new in version 4.1](#whats-new-in-version-41)
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26 | * [What's new in version 4.2](#whats-new-in-version-42)
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27 | * [Constructor options](#constructor-options)
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28 | * [Compatibility modes](#compatibility-modes)
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29 | * [Fetch option](#fetch-option)
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30 | * [Formatting options](#formatting-options)
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31 | * [Inlining options](#inlining-options)
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32 | * [Optimization levels](#optimization-levels)
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33 | + [Level 0 optimizations](#level-0-optimizations)
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34 | + [Level 1 optimizations](#level-1-optimizations)
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35 | + [Level 2 optimizations](#level-2-optimizations)
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36 | * [Minify method](#minify-method)
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37 | * [Promise interface](#promise-interface)
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38 | * [CLI utility](#cli-utility)
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39 | - [FAQ](#faq)
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40 | * [How to optimize multiple files?](#how-to-optimize-multiple-files)
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41 | * [How to process remote `@import`s correctly?](#how-to-process-remote-imports-correctly)
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42 | * [How to apply arbitrary transformations to CSS properties?](#how-to-apply-arbitrary-transformations-to-css-properties)
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43 | * [How to specify a custom rounding precision?](#how-to-specify-a-custom-rounding-precision)
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44 | * [How to keep a CSS fragment intact?](#how-to-keep-a-css-fragment-intact)
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45 | * [How to preserve a comment block?](#how-to-preserve-a-comment-block)
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46 | * [How to rebase relative image URLs?](#how-to-rebase-relative-image-urls)
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47 | * [How to work with source maps?](#how-to-work-with-source-maps)
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48 | * [How to apply level 1 & 2 optimizations at the same time?](#how-to-apply-level-1--2-optimizations-at-the-same-time)
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49 | * [What level 2 optimizations do?](#what-level-2-optimizations-do)
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50 | * [How to use clean-css with build tools?](#how-to-use-clean-css-with-build-tools)
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51 | * [How to use clean-css from web browser?](#how-to-use-clean-css-from-web-browser)
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52 | - [Contributing](#contributing)
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53 | * [How to get started?](#how-to-get-started)
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54 | - [Acknowledgments](#acknowledgments)
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55 | - [License](#license)
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56 |
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57 | # Node.js version support
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58 |
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59 | clean-css requires Node.js 4.0+ (tested on Linux, OS X, and Windows)
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60 |
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61 | # Install
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62 |
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63 | ```
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64 | npm install --save-dev clean-css
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65 | ```
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66 |
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67 | # Use
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68 |
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69 | ```js
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70 | var CleanCSS = require('clean-css');
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71 | var input = 'a{font-weight:bold;}';
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72 | var options = { /* options */ };
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73 | var output = new CleanCSS(options).minify(input);
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74 | ```
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75 |
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76 | ## Important: 4.0 breaking changes
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77 |
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78 | clean-css 4.0 introduces some breaking changes:
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79 |
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80 | * API and CLI interfaces are split, so API stays in this repository while CLI moves to [clean-css-cli](https://github.com/jakubpawlowicz/clean-css-cli);
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81 | * `root`, `relativeTo`, and `target` options are replaced by a single `rebaseTo` option - this means that rebasing URLs and import inlining is much simpler but may not be (YMMV) as powerful as in 3.x;
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82 | * `debug` option is gone as stats are always provided in output object under `stats` property;
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83 | * `roundingPrecision` is disabled by default;
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84 | * `roundingPrecision` applies to **all** units now, not only `px` as in 3.x;
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85 | * `processImport` and `processImportFrom` are merged into `inline` option which defaults to `local`. Remote `@import` rules are **NOT** inlined by default anymore;
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86 | * splits `inliner: { request: ..., timeout: ... }` option into `inlineRequest` and `inlineTimeout` options;
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87 | * remote resources without a protocol, e.g. `//fonts.googleapis.com/css?family=Domine:700`, are not inlined anymore;
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88 | * changes default Internet Explorer compatibility from 9+ to 10+, to revert the old default use `{ compatibility: 'ie9' }` flag;
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89 | * renames `keepSpecialComments` to `specialComments`;
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90 | * moves `roundingPrecision` and `specialComments` to level 1 optimizations options, see examples;
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91 | * moves `mediaMerging`, `restructuring`, `semanticMerging`, and `shorthandCompacting` to level 2 optimizations options, see examples below;
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92 | * renames `shorthandCompacting` option to `mergeIntoShorthands`;
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93 | * level 1 optimizations are the new default, up to 3.x it was level 2;
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94 | * `keepBreaks` option is replaced with `{ format: 'keep-breaks' }` to ease transition;
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95 | * `sourceMap` option has to be a boolean from now on - to specify an input source map pass it a 2nd argument to `minify` method or via a hash instead;
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96 | * `aggressiveMerging` option is removed as aggressive merging is replaced by smarter override merging.
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97 |
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98 | ## What's new in version 4.1
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99 |
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100 | clean-css 4.1 introduces the following changes / features:
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101 |
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102 | * `inline: false` as an alias to `inline: ['none']`;
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103 | * `multiplePseudoMerging` compatibility flag controlling merging of rules with multiple pseudo classes / elements;
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104 | * `removeEmpty` flag in level 1 optimizations controlling removal of rules and nested blocks;
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105 | * `removeEmpty` flag in level 2 optimizations controlling removal of rules and nested blocks;
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106 | * `compatibility: { selectors: { mergeLimit: <number> } }` flag in compatibility settings controlling maximum number of selectors in a single rule;
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107 | * `minify` method improved signature accepting a list of hashes for a predictable traversal;
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108 | * `selectorsSortingMethod` level 1 optimization allows `false` or `'none'` for disabling selector sorting;
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109 | * `fetch` option controlling a function for handling remote requests;
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110 | * new `font` shorthand and `font-*` longhand optimizers;
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111 | * removal of `optimizeFont` flag in level 1 optimizations due to new `font` shorthand optimizer;
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112 | * `skipProperties` flag in level 2 optimizations controlling which properties won't be optimized;
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113 | * new `animation` shorthand and `animation-*` longhand optimizers;
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114 | * `removeUnusedAtRules` level 2 optimization controlling removal of unused `@counter-style`, `@font-face`, `@keyframes`, and `@namespace` at rules;
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115 | * the [web interface](https://jakubpawlowicz.github.io/clean-css) gets an improved settings panel with "reset to defaults", instant option changes, and settings being persisted across sessions.
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116 |
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117 | ## What's new in version 4.2
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118 |
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119 | clean-css 4.2 introduces the following changes / features:
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120 |
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121 | * Adds `process` method for compatibility with optimize-css-assets-webpack-plugin;
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122 | * new `transition` property optimizer;
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123 | * preserves any CSS content between `/* clean-css ignore:start */` and `/* clean-css ignore:end */` comments;
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124 | * allows filtering based on selector in `transform` callback, see [example](#how-to-apply-arbitrary-transformations-to-css-properties);
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125 | * adds configurable line breaks via `format: { breakWith: 'lf' }` option.
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126 |
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127 | ## Constructor options
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128 |
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129 | clean-css constructor accepts a hash as a parameter with the following options available:
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130 |
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131 | * `compatibility` - controls compatibility mode used; defaults to `ie10+`; see [compatibility modes](#compatibility-modes) for examples;
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132 | * `fetch` - controls a function for handling remote requests; see [fetch option](#fetch-option) for examples (since 4.1.0);
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133 | * `format` - controls output CSS formatting; defaults to `false`; see [formatting options](#formatting-options) for examples;
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134 | * `inline` - controls `@import` inlining rules; defaults to `'local'`; see [inlining options](#inlining-options) for examples;
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135 | * `inlineRequest` - controls extra options for inlining remote `@import` rules, can be any of [HTTP(S) request options](https://nodejs.org/api/http.html#http_http_request_options_callback);
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136 | * `inlineTimeout` - controls number of milliseconds after which inlining a remote `@import` fails; defaults to 5000;
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137 | * `level` - controls optimization level used; defaults to `1`; see [optimization levels](#optimization-levels) for examples;
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138 | * `rebase` - controls URL rebasing; defaults to `true`;
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139 | * `rebaseTo` - controls a directory to which all URLs are rebased, most likely the directory under which the output file will live; defaults to the current directory;
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140 | * `returnPromise` - controls whether `minify` method returns a Promise object or not; defaults to `false`; see [promise interface](#promise-interface) for examples;
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141 | * `sourceMap` - controls whether an output source map is built; defaults to `false`;
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142 | * `sourceMapInlineSources` - controls embedding sources inside a source map's `sourcesContent` field; defaults to false.
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143 |
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144 | ## Compatibility modes
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145 |
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146 | There is a certain number of compatibility mode shortcuts, namely:
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147 |
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148 | * `new CleanCSS({ compatibility: '*' })` (default) - Internet Explorer 10+ compatibility mode
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149 | * `new CleanCSS({ compatibility: 'ie9' })` - Internet Explorer 9+ compatibility mode
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150 | * `new CleanCSS({ compatibility: 'ie8' })` - Internet Explorer 8+ compatibility mode
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151 | * `new CleanCSS({ compatibility: 'ie7' })` - Internet Explorer 7+ compatibility mode
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152 |
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153 | Each of these modes is an alias to a [fine grained configuration](https://github.com/jakubpawlowicz/clean-css/blob/master/lib/options/compatibility.js), with the following options available:
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154 |
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155 | ```js
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156 | new CleanCSS({
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157 | compatibility: {
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158 | colors: {
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159 | opacity: true // controls `rgba()` / `hsla()` color support
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160 | },
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161 | properties: {
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162 | backgroundClipMerging: true, // controls background-clip merging into shorthand
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163 | backgroundOriginMerging: true, // controls background-origin merging into shorthand
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164 | backgroundSizeMerging: true, // controls background-size merging into shorthand
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165 | colors: true, // controls color optimizations
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166 | ieBangHack: false, // controls keeping IE bang hack
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167 | ieFilters: false, // controls keeping IE `filter` / `-ms-filter`
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168 | iePrefixHack: false, // controls keeping IE prefix hack
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169 | ieSuffixHack: false, // controls keeping IE suffix hack
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170 | merging: true, // controls property merging based on understandability
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171 | shorterLengthUnits: false, // controls shortening pixel units into `pc`, `pt`, or `in` units
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172 | spaceAfterClosingBrace: true, // controls keeping space after closing brace - `url() no-repeat` into `url()no-repeat`
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173 | urlQuotes: false, // controls keeping quoting inside `url()`
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174 | zeroUnits: true // controls removal of units `0` value
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175 | },
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176 | selectors: {
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177 | adjacentSpace: false, // controls extra space before `nav` element
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178 | ie7Hack: true, // controls removal of IE7 selector hacks, e.g. `*+html...`
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179 | mergeablePseudoClasses: [':active', ...], // controls a whitelist of mergeable pseudo classes
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180 | mergeablePseudoElements: ['::after', ...], // controls a whitelist of mergeable pseudo elements
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181 | mergeLimit: 8191, // controls maximum number of selectors in a single rule (since 4.1.0)
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182 | multiplePseudoMerging: true // controls merging of rules with multiple pseudo classes / elements (since 4.1.0)
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183 | },
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184 | units: {
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185 | ch: true, // controls treating `ch` as a supported unit
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186 | in: true, // controls treating `in` as a supported unit
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187 | pc: true, // controls treating `pc` as a supported unit
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188 | pt: true, // controls treating `pt` as a supported unit
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189 | rem: true, // controls treating `rem` as a supported unit
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190 | vh: true, // controls treating `vh` as a supported unit
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191 | vm: true, // controls treating `vm` as a supported unit
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192 | vmax: true, // controls treating `vmax` as a supported unit
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193 | vmin: true // controls treating `vmin` as a supported unit
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194 | }
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195 | }
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196 | })
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197 | ```
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198 |
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199 | You can also use a string when setting a compatibility mode, e.g.
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200 |
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201 | ```js
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202 | new CleanCSS({
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203 | compatibility: 'ie9,-properties.merging' // sets compatibility to IE9 mode with disabled property merging
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204 | })
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205 | ```
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206 |
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207 | ## Fetch option
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208 |
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209 | The `fetch` option accepts a function which handles remote resource fetching, e.g.
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210 |
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211 | ```js
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212 | var request = require('request');
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213 | var source = '@import url(http://example.com/path/to/stylesheet.css);';
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214 | new CleanCSS({
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215 | fetch: function (uri, inlineRequest, inlineTimeout, callback) {
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216 | request(uri, function (error, response, body) {
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217 | if (error) {
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218 | callback(error, null);
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219 | } else if (response && response.statusCode != 200) {
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220 | callback(response.statusCode, null);
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221 | } else {
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222 | callback(null, body);
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223 | }
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224 | });
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225 | }
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226 | }).minify(source);
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227 | ```
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228 |
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229 | This option provides a convenient way of overriding the default fetching logic if it doesn't support a particular feature, say CONNECT proxies.
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230 |
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231 | Unless given, the default [loadRemoteResource](https://github.com/jakubpawlowicz/clean-css/blob/master/lib/reader/load-remote-resource.js) logic is used.
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232 |
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233 | ## Formatting options
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234 |
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235 | By default output CSS is formatted without any whitespace unless a `format` option is given.
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236 | First of all there are two shorthands:
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237 |
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238 | ```js
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239 | new CleanCSS({
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240 | format: 'beautify' // formats output in a really nice way
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241 | })
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242 | ```
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243 |
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244 | and
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245 |
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246 | ```js
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247 | new CleanCSS({
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248 | format: 'keep-breaks' // formats output the default way but adds line breaks for improved readability
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249 | })
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250 | ```
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251 |
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252 | however `format` option also accept a fine-grained set of options:
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253 |
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254 | ```js
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255 | new CleanCSS({
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256 | format: {
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257 | breaks: { // controls where to insert breaks
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258 | afterAtRule: false, // controls if a line break comes after an at-rule; e.g. `@charset`; defaults to `false`
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259 | afterBlockBegins: false, // controls if a line break comes after a block begins; e.g. `@media`; defaults to `false`
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260 | afterBlockEnds: false, // controls if a line break comes after a block ends, defaults to `false`
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261 | afterComment: false, // controls if a line break comes after a comment; defaults to `false`
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262 | afterProperty: false, // controls if a line break comes after a property; defaults to `false`
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263 | afterRuleBegins: false, // controls if a line break comes after a rule begins; defaults to `false`
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264 | afterRuleEnds: false, // controls if a line break comes after a rule ends; defaults to `false`
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265 | beforeBlockEnds: false, // controls if a line break comes before a block ends; defaults to `false`
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266 | betweenSelectors: false // controls if a line break comes between selectors; defaults to `false`
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267 | },
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268 | breakWith: '\n', // controls the new line character, can be `'\r\n'` or `'\n'` (aliased as `'windows'` and `'unix'` or `'crlf'` and `'lf'`); defaults to system one, so former on Windows and latter on Unix
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269 | indentBy: 0, // controls number of characters to indent with; defaults to `0`
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270 | indentWith: 'space', // controls a character to indent with, can be `'space'` or `'tab'`; defaults to `'space'`
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271 | spaces: { // controls where to insert spaces
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272 | aroundSelectorRelation: false, // controls if spaces come around selector relations; e.g. `div > a`; defaults to `false`
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273 | beforeBlockBegins: false, // controls if a space comes before a block begins; e.g. `.block {`; defaults to `false`
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274 | beforeValue: false // controls if a space comes before a value; e.g. `width: 1rem`; defaults to `false`
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275 | },
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276 | wrapAt: false // controls maximum line length; defaults to `false`
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277 | }
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278 | })
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279 | ```
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280 |
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281 | ## Inlining options
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282 |
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283 | `inline` option whitelists which `@import` rules will be processed, e.g.
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284 |
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285 | ```js
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286 | new CleanCSS({
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287 | inline: ['local'] // default; enables local inlining only
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288 | })
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289 | ```
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290 |
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291 | ```js
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292 | new CleanCSS({
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293 | inline: ['none'] // disables all inlining
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294 | })
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295 | ```
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296 |
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297 | ```js
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298 | // introduced in clean-css 4.1.0
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299 |
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300 | new CleanCSS({
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301 | inline: false // disables all inlining (alias to `['none']`)
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302 | })
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303 | ```
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304 |
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305 | ```js
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306 | new CleanCSS({
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307 | inline: ['all'] // enables all inlining, same as ['local', 'remote']
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308 | })
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309 | ```
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310 |
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311 | ```js
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312 | new CleanCSS({
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313 | inline: ['local', 'mydomain.example.com'] // enables local inlining plus given remote source
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314 | })
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315 | ```
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316 |
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317 | ```js
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318 | new CleanCSS({
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319 | inline: ['local', 'remote', '!fonts.googleapis.com'] // enables all inlining but from given remote source
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320 | })
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321 | ```
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322 |
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323 | ## Optimization levels
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324 |
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325 | The `level` option can be either `0`, `1` (default), or `2`, e.g.
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326 |
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327 | ```js
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328 | new CleanCSS({
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329 | level: 2
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330 | })
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331 | ```
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332 |
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333 | or a fine-grained configuration given via a hash.
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334 |
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335 | Please note that level 1 optimization options are generally safe while level 2 optimizations should be safe for most users.
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336 |
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337 | ### Level 0 optimizations
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338 |
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339 | Level 0 optimizations simply means "no optimizations". Use it when you'd like to inline imports and / or rebase URLs but skip everything else.
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340 |
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341 | ### Level 1 optimizations
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342 |
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343 | Level 1 optimizations (default) operate on single properties only, e.g. can remove units when not required, turn rgb colors to a shorter hex representation, remove comments, etc
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344 |
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345 | Here is a full list of available options:
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346 |
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347 | ```js
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348 | new CleanCSS({
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349 | level: {
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350 | 1: {
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351 | cleanupCharsets: true, // controls `@charset` moving to the front of a stylesheet; defaults to `true`
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352 | normalizeUrls: true, // controls URL normalization; defaults to `true`
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353 | optimizeBackground: true, // controls `background` property optimizations; defaults to `true`
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354 | optimizeBorderRadius: true, // controls `border-radius` property optimizations; defaults to `true`
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355 | optimizeFilter: true, // controls `filter` property optimizations; defaults to `true`
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356 | optimizeFont: true, // controls `font` property optimizations; defaults to `true`
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357 | optimizeFontWeight: true, // controls `font-weight` property optimizations; defaults to `true`
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358 | optimizeOutline: true, // controls `outline` property optimizations; defaults to `true`
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359 | removeEmpty: true, // controls removing empty rules and nested blocks; defaults to `true`
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360 | removeNegativePaddings: true, // controls removing negative paddings; defaults to `true`
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361 | removeQuotes: true, // controls removing quotes when unnecessary; defaults to `true`
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362 | removeWhitespace: true, // controls removing unused whitespace; defaults to `true`
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363 | replaceMultipleZeros: true, // contols removing redundant zeros; defaults to `true`
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364 | replaceTimeUnits: true, // controls replacing time units with shorter values; defaults to `true`
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365 | replaceZeroUnits: true, // controls replacing zero values with units; defaults to `true`
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366 | roundingPrecision: false, // rounds pixel values to `N` decimal places; `false` disables rounding; defaults to `false`
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367 | selectorsSortingMethod: 'standard', // denotes selector sorting method; can be `'natural'` or `'standard'`, `'none'`, or false (the last two since 4.1.0); defaults to `'standard'`
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368 | specialComments: 'all', // denotes a number of /*! ... */ comments preserved; defaults to `all`
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369 | tidyAtRules: true, // controls at-rules (e.g. `@charset`, `@import`) optimizing; defaults to `true`
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370 | tidyBlockScopes: true, // controls block scopes (e.g. `@media`) optimizing; defaults to `true`
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371 | tidySelectors: true, // controls selectors optimizing; defaults to `true`,
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372 | semicolonAfterLastProperty: false, // controls removing trailing semicolons in rule; defaults to `false` - means remove
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373 | transform: function () {} // defines a callback for fine-grained property optimization; defaults to no-op
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374 | }
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375 | }
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376 | });
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377 | ```
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378 |
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379 | There is an `all` shortcut for toggling all options at the same time, e.g.
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380 |
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381 | ```js
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382 | new CleanCSS({
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383 | level: {
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384 | 1: {
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385 | all: false, // set all values to `false`
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386 | tidySelectors: true // turns on optimizing selectors
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387 | }
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388 | }
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389 | });
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390 | ```
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391 |
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392 | ### Level 2 optimizations
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393 |
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394 | Level 2 optimizations operate at rules or multiple properties level, e.g. can remove duplicate rules, remove properties redefined further down a stylesheet, or restructure rules by moving them around.
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395 |
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396 | Please note that if level 2 optimizations are turned on then, unless explicitely disabled, level 1 optimizations are applied as well.
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397 |
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398 | Here is a full list of available options:
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399 |
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400 | ```js
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401 | new CleanCSS({
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402 | level: {
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403 | 2: {
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404 | mergeAdjacentRules: true, // controls adjacent rules merging; defaults to true
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405 | mergeIntoShorthands: true, // controls merging properties into shorthands; defaults to true
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406 | mergeMedia: true, // controls `@media` merging; defaults to true
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407 | mergeNonAdjacentRules: true, // controls non-adjacent rule merging; defaults to true
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408 | mergeSemantically: false, // controls semantic merging; defaults to false
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409 | overrideProperties: true, // controls property overriding based on understandability; defaults to true
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410 | removeEmpty: true, // controls removing empty rules and nested blocks; defaults to `true`
|
411 | reduceNonAdjacentRules: true, // controls non-adjacent rule reducing; defaults to true
|
412 | removeDuplicateFontRules: true, // controls duplicate `@font-face` removing; defaults to true
|
413 | removeDuplicateMediaBlocks: true, // controls duplicate `@media` removing; defaults to true
|
414 | removeDuplicateRules: true, // controls duplicate rules removing; defaults to true
|
415 | removeUnusedAtRules: false, // controls unused at rule removing; defaults to false (available since 4.1.0)
|
416 | restructureRules: false, // controls rule restructuring; defaults to false
|
417 | skipProperties: [] // controls which properties won't be optimized, defaults to `[]` which means all will be optimized (since 4.1.0)
|
418 | }
|
419 | }
|
420 | });
|
421 | ```
|
422 |
|
423 | There is an `all` shortcut for toggling all options at the same time, e.g.
|
424 |
|
425 | ```js
|
426 | new CleanCSS({
|
427 | level: {
|
428 | 2: {
|
429 | all: false, // sets all values to `false`
|
430 | removeDuplicateRules: true // turns on removing duplicate rules
|
431 | }
|
432 | }
|
433 | });
|
434 | ```
|
435 |
|
436 | ## Minify method
|
437 |
|
438 | Once configured clean-css provides a `minify` method to optimize a given CSS, e.g.
|
439 |
|
440 | ```js
|
441 | var output = new CleanCSS(options).minify(source);
|
442 | ```
|
443 |
|
444 | The output of the `minify` method is a hash with following fields:
|
445 |
|
446 | ```js
|
447 | console.log(output.styles); // optimized output CSS as a string
|
448 | console.log(output.sourceMap); // output source map if requested with `sourceMap` option
|
449 | console.log(output.errors); // a list of errors raised
|
450 | console.log(output.warnings); // a list of warnings raised
|
451 | console.log(output.stats.originalSize); // original content size after import inlining
|
452 | console.log(output.stats.minifiedSize); // optimized content size
|
453 | console.log(output.stats.timeSpent); // time spent on optimizations in milliseconds
|
454 | console.log(output.stats.efficiency); // `(originalSize - minifiedSize) / originalSize`, e.g. 0.25 if size is reduced from 100 bytes to 75 bytes
|
455 | ```
|
456 |
|
457 | The `minify` method also accepts an input source map, e.g.
|
458 |
|
459 | ```js
|
460 | var output = new CleanCSS(options).minify(source, inputSourceMap);
|
461 | ```
|
462 |
|
463 | or a callback invoked when optimizations are finished, e.g.
|
464 |
|
465 | ```js
|
466 | new CleanCSS(options).minify(source, function (error, output) {
|
467 | // `output` is the same as in the synchronous call above
|
468 | });
|
469 | ```
|
470 |
|
471 | ## Promise interface
|
472 |
|
473 | If you prefer clean-css to return a Promise object then you need to explicitely ask for it, e.g.
|
474 |
|
475 | ```js
|
476 | new CleanCSS({ returnPromise: true })
|
477 | .minify(source)
|
478 | .then(function (output) { console.log(output.styles); })
|
479 | .catch(function (error) { // deal with errors });
|
480 | ```
|
481 |
|
482 | ## CLI utility
|
483 |
|
484 | Clean-css has an associated command line utility that can be installed separately using `npm install clean-css-cli`. For more detailed information, please visit https://github.com/jakubpawlowicz/clean-css-cli.
|
485 |
|
486 | # FAQ
|
487 |
|
488 | ## How to optimize multiple files?
|
489 |
|
490 | It can be done either by passing an array of paths, or, when sources are already available, a hash or an array of hashes:
|
491 |
|
492 | ```js
|
493 | new CleanCSS().minify(['path/to/file/one', 'path/to/file/two']);
|
494 | ```
|
495 |
|
496 | ```js
|
497 | new CleanCSS().minify({
|
498 | 'path/to/file/one': {
|
499 | styles: 'contents of file one'
|
500 | },
|
501 | 'path/to/file/two': {
|
502 | styles: 'contents of file two'
|
503 | }
|
504 | });
|
505 | ```
|
506 |
|
507 | ```js
|
508 | new CleanCSS().minify([
|
509 | {'path/to/file/one': {styles: 'contents of file one'}},
|
510 | {'path/to/file/two': {styles: 'contents of file two'}}
|
511 | ]);
|
512 | ```
|
513 |
|
514 | Passing an array of hashes allows you to explicitly specify the order in which the input files are concatenated. Whereas when you use a single hash the order is determined by the [traversal order of object properties](http://2ality.com/2015/10/property-traversal-order-es6.html) - available since 4.1.0.
|
515 |
|
516 | Important note - any `@import` rules already present in the hash will be resolved in memory.
|
517 |
|
518 | ## How to process remote `@import`s correctly?
|
519 |
|
520 | In order to inline remote `@import` statements you need to provide a callback to minify method as fetching remote assets is an asynchronous operation, e.g.:
|
521 |
|
522 | ```js
|
523 | var source = '@import url(http://example.com/path/to/remote/styles);';
|
524 | new CleanCSS({ inline: ['remote'] }).minify(source, function (error, output) {
|
525 | // output.styles
|
526 | });
|
527 | ```
|
528 |
|
529 | If you don't provide a callback, then remote `@import`s will be left as is.
|
530 |
|
531 | ## How to apply arbitrary transformations to CSS properties?
|
532 |
|
533 | If clean-css doesn't perform a particular property optimization, you can use `transform` callback to apply it:
|
534 |
|
535 | ```js
|
536 | var source = '.block{background-image:url(/path/to/image.png)}';
|
537 | var output = new CleanCSS({
|
538 | level: {
|
539 | 1: {
|
540 | transform: function (propertyName, propertyValue, selector /* `selector` available since 4.2.0-pre */) {
|
541 | if (propertyName == 'background-image' && propertyValue.indexOf('/path/to') > -1) {
|
542 | return propertyValue.replace('/path/to', '../valid/path/to');
|
543 | }
|
544 | }
|
545 | }
|
546 | }
|
547 | }).minify(source);
|
548 |
|
549 | console.log(output.styles); # => .block{background-image:url(../valid/path/to/image.png)}
|
550 | ```
|
551 |
|
552 | Note: returning `false` from `transform` callback will drop a property.
|
553 |
|
554 | ## How to specify a custom rounding precision?
|
555 |
|
556 | The level 1 `roundingPrecision` optimization option accept a string with per-unit rounding precision settings, e.g.
|
557 |
|
558 | ```js
|
559 | new CleanCSS({
|
560 | level: {
|
561 | 1: {
|
562 | roundingPrecision: 'all=3,px=5'
|
563 | }
|
564 | }
|
565 | }).minify(source)
|
566 | ```
|
567 |
|
568 | which sets all units rounding precision to 3 digits except `px` unit precision of 5 digits.
|
569 |
|
570 | ## How to keep a CSS fragment intact?
|
571 |
|
572 | Note: available in the current master, to be released in 4.2.0.
|
573 |
|
574 | Wrap the CSS fragment in special comments which instruct clean-css to preserve it, e.g.
|
575 |
|
576 | ```css
|
577 | .block-1 {
|
578 | color: red
|
579 | }
|
580 | /* clean-css ignore:start */
|
581 | .block-special {
|
582 | color: transparent
|
583 | }
|
584 | /* clean-css ignore:end */
|
585 | .block-2 {
|
586 | margin: 0
|
587 | }
|
588 | ```
|
589 |
|
590 | Optimizing this CSS will result in the following output:
|
591 |
|
592 | ```css
|
593 | .block-1{color:red}
|
594 | .block-special {
|
595 | color: transparent
|
596 | }
|
597 | .block-2{margin:0}
|
598 | ```
|
599 |
|
600 | ## How to preserve a comment block?
|
601 |
|
602 | Use the `/*!` notation instead of the standard one `/*`:
|
603 |
|
604 | ```css
|
605 | /*!
|
606 | Important comments included in optimized output.
|
607 | */
|
608 | ```
|
609 |
|
610 | ## How to rebase relative image URLs?
|
611 |
|
612 | clean-css will handle it automatically for you in the following cases:
|
613 |
|
614 | * when full paths to input files are passed in as options;
|
615 | * when correct paths are passed in via a hash;
|
616 | * when `rebaseTo` is used with any of above two.
|
617 |
|
618 | ## How to work with source maps?
|
619 |
|
620 | To generate a source map, use `sourceMap: true` option, e.g.:
|
621 |
|
622 | ```js
|
623 | new CleanCSS({ sourceMap: true, rebaseTo: pathToOutputDirectory })
|
624 | .minify(source, function (error, output) {
|
625 | // access output.sourceMap for SourceMapGenerator object
|
626 | // see https://github.com/mozilla/source-map/#sourcemapgenerator for more details
|
627 | });
|
628 | ```
|
629 |
|
630 | You can also pass an input source map directly as a 2nd argument to `minify` method:
|
631 |
|
632 | ```js
|
633 | new CleanCSS({ sourceMap: true, rebaseTo: pathToOutputDirectory })
|
634 | .minify(source, inputSourceMap, function (error, output) {
|
635 | // access output.sourceMap to access SourceMapGenerator object
|
636 | // see https://github.com/mozilla/source-map/#sourcemapgenerator for more details
|
637 | });
|
638 | ```
|
639 |
|
640 | or even multiple input source maps at once:
|
641 |
|
642 | ```js
|
643 | new CleanCSS({ sourceMap: true, rebaseTo: pathToOutputDirectory }).minify({
|
644 | 'path/to/source/1': {
|
645 | styles: '...styles...',
|
646 | sourceMap: '...source-map...'
|
647 | },
|
648 | 'path/to/source/2': {
|
649 | styles: '...styles...',
|
650 | sourceMap: '...source-map...'
|
651 | }
|
652 | }, function (error, output) {
|
653 | // access output.sourceMap as above
|
654 | });
|
655 | ```
|
656 |
|
657 | ## How to apply level 1 & 2 optimizations at the same time?
|
658 |
|
659 | Using the hash configuration specifying both optimization levels, e.g.
|
660 |
|
661 | ```js
|
662 | new CleanCSS({
|
663 | level: {
|
664 | 1: {
|
665 | all: true,
|
666 | normalizeUrls: false
|
667 | },
|
668 | 2: {
|
669 | restructureRules: true
|
670 | }
|
671 | }
|
672 | })
|
673 | ```
|
674 |
|
675 | will apply level 1 optimizations, except url normalization, and default level 2 optimizations with rule restructuring.
|
676 |
|
677 | ## What level 2 optimizations do?
|
678 |
|
679 | All level 2 optimizations are dispatched [here](https://github.com/jakubpawlowicz/clean-css/blob/master/lib/optimizer/level-2/optimize.js#L67), and this is what they do:
|
680 |
|
681 | * `recursivelyOptimizeBlocks` - does all the following operations on a nested block, like `@media` or `@keyframe`;
|
682 | * `recursivelyOptimizeProperties` - optimizes properties in rulesets and flat at-rules, like @font-face, by splitting them into components (e.g. `margin` into `margin-(bottom|left|right|top)`), optimizing, and restoring them back. You may want to use `mergeIntoShorthands` option to control whether you want to turn multiple components into shorthands;
|
683 | * `removeDuplicates` - gets rid of duplicate rulesets with exactly the same set of properties, e.g. when including a Sass / Less partial twice for no good reason;
|
684 | * `mergeAdjacent` - merges adjacent rulesets with the same selector or rules;
|
685 | * `reduceNonAdjacent` - identifies which properties are overridden in same-selector non-adjacent rulesets, and removes them;
|
686 | * `mergeNonAdjacentBySelector` - identifies same-selector non-adjacent rulesets which can be moved (!) to be merged, requires all intermediate rulesets to not redefine the moved properties, or if redefined to have the same value;
|
687 | * `mergeNonAdjacentByBody` - same as the one above but for same-selector non-adjacent rulesets;
|
688 | * `restructure` - tries to reorganize different-selector different-rules rulesets so they take less space, e.g. `.one{padding:0}.two{margin:0}.one{margin-bottom:3px}` into `.two{margin:0}.one{padding:0;margin-bottom:3px}`;
|
689 | * `removeDuplicateFontAtRules` - removes duplicated `@font-face` rules;
|
690 | * `removeDuplicateMediaQueries` - removes duplicated `@media` nested blocks;
|
691 | * `mergeMediaQueries` - merges non-adjacent `@media` at-rules by the same rules as `mergeNonAdjacentBy*` above;
|
692 |
|
693 | ## How to use clean-css with build tools?
|
694 |
|
695 | There is a number of 3rd party plugins to popular build tools:
|
696 |
|
697 | * [Broccoli](https://github.com/broccolijs/broccoli#broccoli): [broccoli-clean-css](https://github.com/shinnn/broccoli-clean-css)
|
698 | * [Brunch](http://brunch.io/): [clean-css-brunch](https://github.com/brunch/clean-css-brunch)
|
699 | * [Grunt](http://gruntjs.com): [grunt-contrib-cssmin](https://github.com/gruntjs/grunt-contrib-cssmin)
|
700 | * [Gulp](http://gulpjs.com/): [gulp-clean-css](https://github.com/scniro/gulp-clean-css)
|
701 | * [Gulp](http://gulpjs.com/): [using vinyl-map as a wrapper - courtesy of @sogko](https://github.com/jakubpawlowicz/clean-css/issues/342)
|
702 | * [component-builder2](https://github.com/component/builder2.js): [builder-clean-css](https://github.com/poying/builder-clean-css)
|
703 | * [Metalsmith](http://metalsmith.io): [metalsmith-clean-css](https://github.com/aymericbeaumet/metalsmith-clean-css)
|
704 | * [Lasso](https://github.com/lasso-js/lasso): [lasso-clean-css](https://github.com/yomed/lasso-clean-css)
|
705 | * [Start](https://github.com/start-runner/start): [start-clean-css](https://github.com/start-runner/clean-css)
|
706 |
|
707 | ## How to use clean-css from web browser?
|
708 |
|
709 | * https://jakubpawlowicz.github.io/clean-css/ (official web interface)
|
710 | * http://refresh-sf.com/
|
711 | * http://adamburgess.github.io/clean-css-online/
|
712 |
|
713 | # Contributing
|
714 |
|
715 | See [CONTRIBUTING.md](https://github.com/jakubpawlowicz/clean-css/blob/master/CONTRIBUTING.md).
|
716 |
|
717 | ## How to get started?
|
718 |
|
719 | First clone the sources:
|
720 |
|
721 | ```bash
|
722 | git clone git@github.com:jakubpawlowicz/clean-css.git
|
723 | ```
|
724 |
|
725 | then install dependencies:
|
726 |
|
727 | ```bash
|
728 | cd clean-css
|
729 | npm install
|
730 | ```
|
731 |
|
732 | then use any of the following commands to verify your copy:
|
733 |
|
734 | ```bash
|
735 | npm run bench # for clean-css benchmarks (see [test/bench.js](https://github.com/jakubpawlowicz/clean-css/blob/master/test/bench.js) for details)
|
736 | npm run browserify # to create the browser-ready clean-css version
|
737 | npm run check # to lint JS sources with [JSHint](https://github.com/jshint/jshint/)
|
738 | npm test # to run all tests
|
739 | ```
|
740 |
|
741 | # Acknowledgments
|
742 |
|
743 | Sorted alphabetically by GitHub handle:
|
744 |
|
745 | * [@abarre](https://github.com/abarre) (Anthony Barre) for improvements to `@import` processing;
|
746 | * [@alexlamsl](https://github.com/alexlamsl) (Alex Lam S.L.) for testing early clean-css 4 versions, reporting bugs, and suggesting numerous improvements.
|
747 | * [@altschuler](https://github.com/altschuler) (Simon Altschuler) for fixing `@import` processing inside comments;
|
748 | * [@ben-eb](https://github.com/ben-eb) (Ben Briggs) for sharing ideas about CSS optimizations;
|
749 | * [@davisjam](https://github.com/davisjam) (Jamie Davis) for disclosing ReDOS vulnerabilities;
|
750 | * [@facelessuser](https://github.com/facelessuser) (Isaac) for pointing out a flaw in clean-css' stateless mode;
|
751 | * [@grandrath](https://github.com/grandrath) (Martin Grandrath) for improving `minify` method source traversal in ES6;
|
752 | * [@jmalonzo](https://github.com/jmalonzo) (Jan Michael Alonzo) for a patch removing node.js' old `sys` package;
|
753 | * [@lukeapage](https://github.com/lukeapage) (Luke Page) for suggestions and testing the source maps feature;
|
754 | Plus everyone else involved in [#125](https://github.com/jakubpawlowicz/clean-css/issues/125) for pushing it forward;
|
755 | * [@madwizard-thomas](https://github.com/madwizard-thomas) for sharing ideas about `@import` inlining and URL rebasing.
|
756 | * [@ngyikp](https://github.com/ngyikp) (Ng Yik Phang) for testing early clean-css 4 versions, reporting bugs, and suggesting numerous improvements.
|
757 | * [@wagenet](https://github.com/wagenet) (Peter Wagenet) for suggesting improvements to `@import` inlining behavior;
|
758 | * [@venemo](https://github.com/venemo) (Timur Kristóf) for an outstanding contribution of advanced property optimizer for 2.2 release;
|
759 | * [@vvo](https://github.com/vvo) (Vincent Voyer) for a patch with better empty element regex and for inspiring us to do many performance improvements in 0.4 release;
|
760 | * [@xhmikosr](https://github.com/xhmikosr) for suggesting new features, like option to remove special comments and strip out URLs quotation, and pointing out numerous improvements like JSHint, media queries, etc.
|
761 |
|
762 | # License
|
763 |
|
764 | clean-css is released under the [MIT License](https://github.com/jakubpawlowicz/clean-css/blob/master/LICENSE).
|