765 lines
34 KiB
Markdown
765 lines
34 KiB
Markdown
<h1 align="center">
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<br/>
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<img src="https://cdn.rawgit.com/jakubpawlowicz/clean-css/master/logo.v2.svg" alt="clean-css logo" width="525px"/>
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<br/>
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<br/>
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</h1>
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[](https://www.npmjs.com/package/clean-css)
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[](https://travis-ci.org/jakubpawlowicz/clean-css)
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[](https://ci.appveyor.com/project/jakubpawlowicz/clean-css/branch/master)
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[](https://david-dm.org/jakubpawlowicz/clean-css)
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[](https://npmcharts.com/compare/clean-css?minimal=true)
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[](https://twitter.com/cleancss)
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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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According to [tests](http://goalsmashers.github.io/css-minification-benchmark/) it is one of the best available.
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**Table of Contents**
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- [Node.js version support](#nodejs-version-support)
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- [Install](#install)
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- [Use](#use)
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* [Important: 4.0 breaking changes](#important-40-breaking-changes)
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* [What's new in version 4.1](#whats-new-in-version-41)
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* [What's new in version 4.2](#whats-new-in-version-42)
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* [Constructor options](#constructor-options)
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* [Compatibility modes](#compatibility-modes)
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* [Fetch option](#fetch-option)
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* [Formatting options](#formatting-options)
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* [Inlining options](#inlining-options)
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* [Optimization levels](#optimization-levels)
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+ [Level 0 optimizations](#level-0-optimizations)
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+ [Level 1 optimizations](#level-1-optimizations)
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+ [Level 2 optimizations](#level-2-optimizations)
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* [Minify method](#minify-method)
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* [Promise interface](#promise-interface)
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* [CLI utility](#cli-utility)
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- [FAQ](#faq)
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* [How to optimize multiple files?](#how-to-optimize-multiple-files)
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* [How to process remote `@import`s correctly?](#how-to-process-remote-imports-correctly)
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* [How to apply arbitrary transformations to CSS properties?](#how-to-apply-arbitrary-transformations-to-css-properties)
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* [How to specify a custom rounding precision?](#how-to-specify-a-custom-rounding-precision)
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* [How to keep a CSS fragment intact?](#how-to-keep-a-css-fragment-intact)
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* [How to preserve a comment block?](#how-to-preserve-a-comment-block)
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* [How to rebase relative image URLs?](#how-to-rebase-relative-image-urls)
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* [How to work with source maps?](#how-to-work-with-source-maps)
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* [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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* [What level 2 optimizations do?](#what-level-2-optimizations-do)
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* [How to use clean-css with build tools?](#how-to-use-clean-css-with-build-tools)
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* [How to use clean-css from web browser?](#how-to-use-clean-css-from-web-browser)
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- [Contributing](#contributing)
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* [How to get started?](#how-to-get-started)
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- [Acknowledgments](#acknowledgments)
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- [License](#license)
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# Node.js version support
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clean-css requires Node.js 4.0+ (tested on Linux, OS X, and Windows)
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# Install
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```
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npm install --save-dev clean-css
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```
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# Use
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```js
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var CleanCSS = require('clean-css');
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var input = 'a{font-weight:bold;}';
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var options = { /* options */ };
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var output = new CleanCSS(options).minify(input);
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```
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## Important: 4.0 breaking changes
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clean-css 4.0 introduces some breaking changes:
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* 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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* `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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* `debug` option is gone as stats are always provided in output object under `stats` property;
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* `roundingPrecision` is disabled by default;
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* `roundingPrecision` applies to **all** units now, not only `px` as in 3.x;
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* `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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* splits `inliner: { request: ..., timeout: ... }` option into `inlineRequest` and `inlineTimeout` options;
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* remote resources without a protocol, e.g. `//fonts.googleapis.com/css?family=Domine:700`, are not inlined anymore;
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* changes default Internet Explorer compatibility from 9+ to 10+, to revert the old default use `{ compatibility: 'ie9' }` flag;
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* renames `keepSpecialComments` to `specialComments`;
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* moves `roundingPrecision` and `specialComments` to level 1 optimizations options, see examples;
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* moves `mediaMerging`, `restructuring`, `semanticMerging`, and `shorthandCompacting` to level 2 optimizations options, see examples below;
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* renames `shorthandCompacting` option to `mergeIntoShorthands`;
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* level 1 optimizations are the new default, up to 3.x it was level 2;
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* `keepBreaks` option is replaced with `{ format: 'keep-breaks' }` to ease transition;
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* `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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* `aggressiveMerging` option is removed as aggressive merging is replaced by smarter override merging.
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## What's new in version 4.1
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clean-css 4.1 introduces the following changes / features:
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* `inline: false` as an alias to `inline: ['none']`;
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* `multiplePseudoMerging` compatibility flag controlling merging of rules with multiple pseudo classes / elements;
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* `removeEmpty` flag in level 1 optimizations controlling removal of rules and nested blocks;
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* `removeEmpty` flag in level 2 optimizations controlling removal of rules and nested blocks;
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* `compatibility: { selectors: { mergeLimit: <number> } }` flag in compatibility settings controlling maximum number of selectors in a single rule;
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* `minify` method improved signature accepting a list of hashes for a predictable traversal;
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* `selectorsSortingMethod` level 1 optimization allows `false` or `'none'` for disabling selector sorting;
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* `fetch` option controlling a function for handling remote requests;
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* new `font` shorthand and `font-*` longhand optimizers;
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* removal of `optimizeFont` flag in level 1 optimizations due to new `font` shorthand optimizer;
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* `skipProperties` flag in level 2 optimizations controlling which properties won't be optimized;
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* new `animation` shorthand and `animation-*` longhand optimizers;
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* `removeUnusedAtRules` level 2 optimization controlling removal of unused `@counter-style`, `@font-face`, `@keyframes`, and `@namespace` at rules;
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* 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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## What's new in version 4.2
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clean-css 4.2 introduces the following changes / features:
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* Adds `process` method for compatibility with optimize-css-assets-webpack-plugin;
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* new `transition` property optimizer;
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* preserves any CSS content between `/* clean-css ignore:start */` and `/* clean-css ignore:end */` comments;
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* allows filtering based on selector in `transform` callback, see [example](#how-to-apply-arbitrary-transformations-to-css-properties);
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* adds configurable line breaks via `format: { breakWith: 'lf' }` option.
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## Constructor options
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clean-css constructor accepts a hash as a parameter with the following options available:
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* `compatibility` - controls compatibility mode used; defaults to `ie10+`; see [compatibility modes](#compatibility-modes) for examples;
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* `fetch` - controls a function for handling remote requests; see [fetch option](#fetch-option) for examples (since 4.1.0);
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* `format` - controls output CSS formatting; defaults to `false`; see [formatting options](#formatting-options) for examples;
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* `inline` - controls `@import` inlining rules; defaults to `'local'`; see [inlining options](#inlining-options) for examples;
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* `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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* `inlineTimeout` - controls number of milliseconds after which inlining a remote `@import` fails; defaults to 5000;
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* `level` - controls optimization level used; defaults to `1`; see [optimization levels](#optimization-levels) for examples;
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* `rebase` - controls URL rebasing; defaults to `true`;
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* `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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* `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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* `sourceMap` - controls whether an output source map is built; defaults to `false`;
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* `sourceMapInlineSources` - controls embedding sources inside a source map's `sourcesContent` field; defaults to false.
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## Compatibility modes
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There is a certain number of compatibility mode shortcuts, namely:
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* `new CleanCSS({ compatibility: '*' })` (default) - Internet Explorer 10+ compatibility mode
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* `new CleanCSS({ compatibility: 'ie9' })` - Internet Explorer 9+ compatibility mode
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* `new CleanCSS({ compatibility: 'ie8' })` - Internet Explorer 8+ compatibility mode
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* `new CleanCSS({ compatibility: 'ie7' })` - Internet Explorer 7+ compatibility mode
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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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```js
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new CleanCSS({
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compatibility: {
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colors: {
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opacity: true // controls `rgba()` / `hsla()` color support
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},
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properties: {
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backgroundClipMerging: true, // controls background-clip merging into shorthand
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backgroundOriginMerging: true, // controls background-origin merging into shorthand
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backgroundSizeMerging: true, // controls background-size merging into shorthand
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colors: true, // controls color optimizations
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ieBangHack: false, // controls keeping IE bang hack
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ieFilters: false, // controls keeping IE `filter` / `-ms-filter`
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iePrefixHack: false, // controls keeping IE prefix hack
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ieSuffixHack: false, // controls keeping IE suffix hack
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merging: true, // controls property merging based on understandability
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shorterLengthUnits: false, // controls shortening pixel units into `pc`, `pt`, or `in` units
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spaceAfterClosingBrace: true, // controls keeping space after closing brace - `url() no-repeat` into `url()no-repeat`
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urlQuotes: false, // controls keeping quoting inside `url()`
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zeroUnits: true // controls removal of units `0` value
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},
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selectors: {
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adjacentSpace: false, // controls extra space before `nav` element
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ie7Hack: true, // controls removal of IE7 selector hacks, e.g. `*+html...`
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mergeablePseudoClasses: [':active', ...], // controls a whitelist of mergeable pseudo classes
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mergeablePseudoElements: ['::after', ...], // controls a whitelist of mergeable pseudo elements
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mergeLimit: 8191, // controls maximum number of selectors in a single rule (since 4.1.0)
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multiplePseudoMerging: true // controls merging of rules with multiple pseudo classes / elements (since 4.1.0)
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},
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units: {
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ch: true, // controls treating `ch` as a supported unit
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in: true, // controls treating `in` as a supported unit
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pc: true, // controls treating `pc` as a supported unit
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pt: true, // controls treating `pt` as a supported unit
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rem: true, // controls treating `rem` as a supported unit
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vh: true, // controls treating `vh` as a supported unit
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vm: true, // controls treating `vm` as a supported unit
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vmax: true, // controls treating `vmax` as a supported unit
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vmin: true // controls treating `vmin` as a supported unit
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}
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}
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})
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```
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You can also use a string when setting a compatibility mode, e.g.
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```js
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new CleanCSS({
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compatibility: 'ie9,-properties.merging' // sets compatibility to IE9 mode with disabled property merging
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})
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```
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## Fetch option
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The `fetch` option accepts a function which handles remote resource fetching, e.g.
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```js
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var request = require('request');
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var source = '@import url(http://example.com/path/to/stylesheet.css);';
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new CleanCSS({
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fetch: function (uri, inlineRequest, inlineTimeout, callback) {
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request(uri, function (error, response, body) {
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if (error) {
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callback(error, null);
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} else if (response && response.statusCode != 200) {
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callback(response.statusCode, null);
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} else {
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callback(null, body);
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}
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});
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}
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}).minify(source);
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```
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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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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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## Formatting options
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By default output CSS is formatted without any whitespace unless a `format` option is given.
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First of all there are two shorthands:
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```js
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new CleanCSS({
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format: 'beautify' // formats output in a really nice way
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})
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```
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and
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```js
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new CleanCSS({
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format: 'keep-breaks' // formats output the default way but adds line breaks for improved readability
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})
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```
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however `format` option also accept a fine-grained set of options:
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```js
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new CleanCSS({
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format: {
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breaks: { // controls where to insert breaks
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afterAtRule: false, // controls if a line break comes after an at-rule; e.g. `@charset`; defaults to `false`
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afterBlockBegins: false, // controls if a line break comes after a block begins; e.g. `@media`; defaults to `false`
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afterBlockEnds: false, // controls if a line break comes after a block ends, defaults to `false`
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afterComment: false, // controls if a line break comes after a comment; defaults to `false`
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afterProperty: false, // controls if a line break comes after a property; defaults to `false`
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afterRuleBegins: false, // controls if a line break comes after a rule begins; defaults to `false`
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afterRuleEnds: false, // controls if a line break comes after a rule ends; defaults to `false`
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beforeBlockEnds: false, // controls if a line break comes before a block ends; defaults to `false`
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betweenSelectors: false // controls if a line break comes between selectors; defaults to `false`
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},
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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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indentBy: 0, // controls number of characters to indent with; defaults to `0`
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indentWith: 'space', // controls a character to indent with, can be `'space'` or `'tab'`; defaults to `'space'`
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spaces: { // controls where to insert spaces
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aroundSelectorRelation: false, // controls if spaces come around selector relations; e.g. `div > a`; defaults to `false`
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beforeBlockBegins: false, // controls if a space comes before a block begins; e.g. `.block {`; defaults to `false`
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beforeValue: false // controls if a space comes before a value; e.g. `width: 1rem`; defaults to `false`
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},
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wrapAt: false // controls maximum line length; defaults to `false`
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}
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})
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```
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## Inlining options
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`inline` option whitelists which `@import` rules will be processed, e.g.
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```js
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new CleanCSS({
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inline: ['local'] // default; enables local inlining only
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})
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```
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```js
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new CleanCSS({
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inline: ['none'] // disables all inlining
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})
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```
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```js
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// introduced in clean-css 4.1.0
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new CleanCSS({
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inline: false // disables all inlining (alias to `['none']`)
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})
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```
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```js
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new CleanCSS({
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inline: ['all'] // enables all inlining, same as ['local', 'remote']
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})
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```
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```js
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new CleanCSS({
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inline: ['local', 'mydomain.example.com'] // enables local inlining plus given remote source
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})
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```
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```js
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new CleanCSS({
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inline: ['local', 'remote', '!fonts.googleapis.com'] // enables all inlining but from given remote source
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})
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```
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## Optimization levels
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The `level` option can be either `0`, `1` (default), or `2`, e.g.
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```js
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new CleanCSS({
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level: 2
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})
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```
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or a fine-grained configuration given via a hash.
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Please note that level 1 optimization options are generally safe while level 2 optimizations should be safe for most users.
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### Level 0 optimizations
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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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### Level 1 optimizations
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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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Here is a full list of available options:
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```js
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new CleanCSS({
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level: {
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1: {
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cleanupCharsets: true, // controls `@charset` moving to the front of a stylesheet; defaults to `true`
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normalizeUrls: true, // controls URL normalization; defaults to `true`
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optimizeBackground: true, // controls `background` property optimizations; defaults to `true`
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optimizeBorderRadius: true, // controls `border-radius` property optimizations; defaults to `true`
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optimizeFilter: true, // controls `filter` property optimizations; defaults to `true`
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optimizeFont: true, // controls `font` property optimizations; defaults to `true`
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optimizeFontWeight: true, // controls `font-weight` property optimizations; defaults to `true`
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optimizeOutline: true, // controls `outline` property optimizations; defaults to `true`
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removeEmpty: true, // controls removing empty rules and nested blocks; defaults to `true`
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removeNegativePaddings: true, // controls removing negative paddings; defaults to `true`
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removeQuotes: true, // controls removing quotes when unnecessary; defaults to `true`
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removeWhitespace: true, // controls removing unused whitespace; defaults to `true`
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replaceMultipleZeros: true, // contols removing redundant zeros; defaults to `true`
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replaceTimeUnits: true, // controls replacing time units with shorter values; defaults to `true`
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replaceZeroUnits: true, // controls replacing zero values with units; defaults to `true`
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roundingPrecision: false, // rounds pixel values to `N` decimal places; `false` disables rounding; defaults to `false`
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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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specialComments: 'all', // denotes a number of /*! ... */ comments preserved; defaults to `all`
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tidyAtRules: true, // controls at-rules (e.g. `@charset`, `@import`) optimizing; defaults to `true`
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tidyBlockScopes: true, // controls block scopes (e.g. `@media`) optimizing; defaults to `true`
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tidySelectors: true, // controls selectors optimizing; defaults to `true`,
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semicolonAfterLastProperty: false, // controls removing trailing semicolons in rule; defaults to `false` - means remove
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transform: function () {} // defines a callback for fine-grained property optimization; defaults to no-op
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}
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}
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});
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```
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There is an `all` shortcut for toggling all options at the same time, e.g.
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```js
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new CleanCSS({
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level: {
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1: {
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all: false, // set all values to `false`
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tidySelectors: true // turns on optimizing selectors
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}
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}
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});
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```
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### Level 2 optimizations
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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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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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Here is a full list of available options:
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```js
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new CleanCSS({
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level: {
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2: {
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mergeAdjacentRules: true, // controls adjacent rules merging; defaults to true
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mergeIntoShorthands: true, // controls merging properties into shorthands; defaults to true
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mergeMedia: true, // controls `@media` merging; defaults to true
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mergeNonAdjacentRules: true, // controls non-adjacent rule merging; defaults to true
|
|
mergeSemantically: false, // controls semantic merging; defaults to false
|
|
overrideProperties: true, // controls property overriding based on understandability; defaults to true
|
|
removeEmpty: true, // controls removing empty rules and nested blocks; defaults to `true`
|
|
reduceNonAdjacentRules: true, // controls non-adjacent rule reducing; defaults to true
|
|
removeDuplicateFontRules: true, // controls duplicate `@font-face` removing; defaults to true
|
|
removeDuplicateMediaBlocks: true, // controls duplicate `@media` removing; defaults to true
|
|
removeDuplicateRules: true, // controls duplicate rules removing; defaults to true
|
|
removeUnusedAtRules: false, // controls unused at rule removing; defaults to false (available since 4.1.0)
|
|
restructureRules: false, // controls rule restructuring; defaults to false
|
|
skipProperties: [] // controls which properties won't be optimized, defaults to `[]` which means all will be optimized (since 4.1.0)
|
|
}
|
|
}
|
|
});
|
|
```
|
|
|
|
There is an `all` shortcut for toggling all options at the same time, e.g.
|
|
|
|
```js
|
|
new CleanCSS({
|
|
level: {
|
|
2: {
|
|
all: false, // sets all values to `false`
|
|
removeDuplicateRules: true // turns on removing duplicate rules
|
|
}
|
|
}
|
|
});
|
|
```
|
|
|
|
## Minify method
|
|
|
|
Once configured clean-css provides a `minify` method to optimize a given CSS, e.g.
|
|
|
|
```js
|
|
var output = new CleanCSS(options).minify(source);
|
|
```
|
|
|
|
The output of the `minify` method is a hash with following fields:
|
|
|
|
```js
|
|
console.log(output.styles); // optimized output CSS as a string
|
|
console.log(output.sourceMap); // output source map if requested with `sourceMap` option
|
|
console.log(output.errors); // a list of errors raised
|
|
console.log(output.warnings); // a list of warnings raised
|
|
console.log(output.stats.originalSize); // original content size after import inlining
|
|
console.log(output.stats.minifiedSize); // optimized content size
|
|
console.log(output.stats.timeSpent); // time spent on optimizations in milliseconds
|
|
console.log(output.stats.efficiency); // `(originalSize - minifiedSize) / originalSize`, e.g. 0.25 if size is reduced from 100 bytes to 75 bytes
|
|
```
|
|
|
|
The `minify` method also accepts an input source map, e.g.
|
|
|
|
```js
|
|
var output = new CleanCSS(options).minify(source, inputSourceMap);
|
|
```
|
|
|
|
or a callback invoked when optimizations are finished, e.g.
|
|
|
|
```js
|
|
new CleanCSS(options).minify(source, function (error, output) {
|
|
// `output` is the same as in the synchronous call above
|
|
});
|
|
```
|
|
|
|
## Promise interface
|
|
|
|
If you prefer clean-css to return a Promise object then you need to explicitely ask for it, e.g.
|
|
|
|
```js
|
|
new CleanCSS({ returnPromise: true })
|
|
.minify(source)
|
|
.then(function (output) { console.log(output.styles); })
|
|
.catch(function (error) { // deal with errors });
|
|
```
|
|
|
|
## CLI utility
|
|
|
|
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.
|
|
|
|
# FAQ
|
|
|
|
## How to optimize multiple files?
|
|
|
|
It can be done either by passing an array of paths, or, when sources are already available, a hash or an array of hashes:
|
|
|
|
```js
|
|
new CleanCSS().minify(['path/to/file/one', 'path/to/file/two']);
|
|
```
|
|
|
|
```js
|
|
new CleanCSS().minify({
|
|
'path/to/file/one': {
|
|
styles: 'contents of file one'
|
|
},
|
|
'path/to/file/two': {
|
|
styles: 'contents of file two'
|
|
}
|
|
});
|
|
```
|
|
|
|
```js
|
|
new CleanCSS().minify([
|
|
{'path/to/file/one': {styles: 'contents of file one'}},
|
|
{'path/to/file/two': {styles: 'contents of file two'}}
|
|
]);
|
|
```
|
|
|
|
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.
|
|
|
|
Important note - any `@import` rules already present in the hash will be resolved in memory.
|
|
|
|
## How to process remote `@import`s correctly?
|
|
|
|
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.:
|
|
|
|
```js
|
|
var source = '@import url(http://example.com/path/to/remote/styles);';
|
|
new CleanCSS({ inline: ['remote'] }).minify(source, function (error, output) {
|
|
// output.styles
|
|
});
|
|
```
|
|
|
|
If you don't provide a callback, then remote `@import`s will be left as is.
|
|
|
|
## How to apply arbitrary transformations to CSS properties?
|
|
|
|
If clean-css doesn't perform a particular property optimization, you can use `transform` callback to apply it:
|
|
|
|
```js
|
|
var source = '.block{background-image:url(/path/to/image.png)}';
|
|
var output = new CleanCSS({
|
|
level: {
|
|
1: {
|
|
transform: function (propertyName, propertyValue, selector /* `selector` available since 4.2.0-pre */) {
|
|
if (propertyName == 'background-image' && propertyValue.indexOf('/path/to') > -1) {
|
|
return propertyValue.replace('/path/to', '../valid/path/to');
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}).minify(source);
|
|
|
|
console.log(output.styles); # => .block{background-image:url(../valid/path/to/image.png)}
|
|
```
|
|
|
|
Note: returning `false` from `transform` callback will drop a property.
|
|
|
|
## How to specify a custom rounding precision?
|
|
|
|
The level 1 `roundingPrecision` optimization option accept a string with per-unit rounding precision settings, e.g.
|
|
|
|
```js
|
|
new CleanCSS({
|
|
level: {
|
|
1: {
|
|
roundingPrecision: 'all=3,px=5'
|
|
}
|
|
}
|
|
}).minify(source)
|
|
```
|
|
|
|
which sets all units rounding precision to 3 digits except `px` unit precision of 5 digits.
|
|
|
|
## How to keep a CSS fragment intact?
|
|
|
|
Note: available in the current master, to be released in 4.2.0.
|
|
|
|
Wrap the CSS fragment in special comments which instruct clean-css to preserve it, e.g.
|
|
|
|
```css
|
|
.block-1 {
|
|
color: red
|
|
}
|
|
/* clean-css ignore:start */
|
|
.block-special {
|
|
color: transparent
|
|
}
|
|
/* clean-css ignore:end */
|
|
.block-2 {
|
|
margin: 0
|
|
}
|
|
```
|
|
|
|
Optimizing this CSS will result in the following output:
|
|
|
|
```css
|
|
.block-1{color:red}
|
|
.block-special {
|
|
color: transparent
|
|
}
|
|
.block-2{margin:0}
|
|
```
|
|
|
|
## How to preserve a comment block?
|
|
|
|
Use the `/*!` notation instead of the standard one `/*`:
|
|
|
|
```css
|
|
/*!
|
|
Important comments included in optimized output.
|
|
*/
|
|
```
|
|
|
|
## How to rebase relative image URLs?
|
|
|
|
clean-css will handle it automatically for you in the following cases:
|
|
|
|
* when full paths to input files are passed in as options;
|
|
* when correct paths are passed in via a hash;
|
|
* when `rebaseTo` is used with any of above two.
|
|
|
|
## How to work with source maps?
|
|
|
|
To generate a source map, use `sourceMap: true` option, e.g.:
|
|
|
|
```js
|
|
new CleanCSS({ sourceMap: true, rebaseTo: pathToOutputDirectory })
|
|
.minify(source, function (error, output) {
|
|
// access output.sourceMap for SourceMapGenerator object
|
|
// see https://github.com/mozilla/source-map/#sourcemapgenerator for more details
|
|
});
|
|
```
|
|
|
|
You can also pass an input source map directly as a 2nd argument to `minify` method:
|
|
|
|
```js
|
|
new CleanCSS({ sourceMap: true, rebaseTo: pathToOutputDirectory })
|
|
.minify(source, inputSourceMap, function (error, output) {
|
|
// access output.sourceMap to access SourceMapGenerator object
|
|
// see https://github.com/mozilla/source-map/#sourcemapgenerator for more details
|
|
});
|
|
```
|
|
|
|
or even multiple input source maps at once:
|
|
|
|
```js
|
|
new CleanCSS({ sourceMap: true, rebaseTo: pathToOutputDirectory }).minify({
|
|
'path/to/source/1': {
|
|
styles: '...styles...',
|
|
sourceMap: '...source-map...'
|
|
},
|
|
'path/to/source/2': {
|
|
styles: '...styles...',
|
|
sourceMap: '...source-map...'
|
|
}
|
|
}, function (error, output) {
|
|
// access output.sourceMap as above
|
|
});
|
|
```
|
|
|
|
## How to apply level 1 & 2 optimizations at the same time?
|
|
|
|
Using the hash configuration specifying both optimization levels, e.g.
|
|
|
|
```js
|
|
new CleanCSS({
|
|
level: {
|
|
1: {
|
|
all: true,
|
|
normalizeUrls: false
|
|
},
|
|
2: {
|
|
restructureRules: true
|
|
}
|
|
}
|
|
})
|
|
```
|
|
|
|
will apply level 1 optimizations, except url normalization, and default level 2 optimizations with rule restructuring.
|
|
|
|
## What level 2 optimizations do?
|
|
|
|
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:
|
|
|
|
* `recursivelyOptimizeBlocks` - does all the following operations on a nested block, like `@media` or `@keyframe`;
|
|
* `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;
|
|
* `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;
|
|
* `mergeAdjacent` - merges adjacent rulesets with the same selector or rules;
|
|
* `reduceNonAdjacent` - identifies which properties are overridden in same-selector non-adjacent rulesets, and removes them;
|
|
* `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;
|
|
* `mergeNonAdjacentByBody` - same as the one above but for same-selector non-adjacent rulesets;
|
|
* `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}`;
|
|
* `removeDuplicateFontAtRules` - removes duplicated `@font-face` rules;
|
|
* `removeDuplicateMediaQueries` - removes duplicated `@media` nested blocks;
|
|
* `mergeMediaQueries` - merges non-adjacent `@media` at-rules by the same rules as `mergeNonAdjacentBy*` above;
|
|
|
|
## How to use clean-css with build tools?
|
|
|
|
There is a number of 3rd party plugins to popular build tools:
|
|
|
|
* [Broccoli](https://github.com/broccolijs/broccoli#broccoli): [broccoli-clean-css](https://github.com/shinnn/broccoli-clean-css)
|
|
* [Brunch](http://brunch.io/): [clean-css-brunch](https://github.com/brunch/clean-css-brunch)
|
|
* [Grunt](http://gruntjs.com): [grunt-contrib-cssmin](https://github.com/gruntjs/grunt-contrib-cssmin)
|
|
* [Gulp](http://gulpjs.com/): [gulp-clean-css](https://github.com/scniro/gulp-clean-css)
|
|
* [Gulp](http://gulpjs.com/): [using vinyl-map as a wrapper - courtesy of @sogko](https://github.com/jakubpawlowicz/clean-css/issues/342)
|
|
* [component-builder2](https://github.com/component/builder2.js): [builder-clean-css](https://github.com/poying/builder-clean-css)
|
|
* [Metalsmith](http://metalsmith.io): [metalsmith-clean-css](https://github.com/aymericbeaumet/metalsmith-clean-css)
|
|
* [Lasso](https://github.com/lasso-js/lasso): [lasso-clean-css](https://github.com/yomed/lasso-clean-css)
|
|
* [Start](https://github.com/start-runner/start): [start-clean-css](https://github.com/start-runner/clean-css)
|
|
|
|
## How to use clean-css from web browser?
|
|
|
|
* https://jakubpawlowicz.github.io/clean-css/ (official web interface)
|
|
* http://refresh-sf.com/
|
|
* http://adamburgess.github.io/clean-css-online/
|
|
|
|
# Contributing
|
|
|
|
See [CONTRIBUTING.md](https://github.com/jakubpawlowicz/clean-css/blob/master/CONTRIBUTING.md).
|
|
|
|
## How to get started?
|
|
|
|
First clone the sources:
|
|
|
|
```bash
|
|
git clone git@github.com:jakubpawlowicz/clean-css.git
|
|
```
|
|
|
|
then install dependencies:
|
|
|
|
```bash
|
|
cd clean-css
|
|
npm install
|
|
```
|
|
|
|
then use any of the following commands to verify your copy:
|
|
|
|
```bash
|
|
npm run bench # for clean-css benchmarks (see [test/bench.js](https://github.com/jakubpawlowicz/clean-css/blob/master/test/bench.js) for details)
|
|
npm run browserify # to create the browser-ready clean-css version
|
|
npm run check # to lint JS sources with [JSHint](https://github.com/jshint/jshint/)
|
|
npm test # to run all tests
|
|
```
|
|
|
|
# Acknowledgments
|
|
|
|
Sorted alphabetically by GitHub handle:
|
|
|
|
* [@abarre](https://github.com/abarre) (Anthony Barre) for improvements to `@import` processing;
|
|
* [@alexlamsl](https://github.com/alexlamsl) (Alex Lam S.L.) for testing early clean-css 4 versions, reporting bugs, and suggesting numerous improvements.
|
|
* [@altschuler](https://github.com/altschuler) (Simon Altschuler) for fixing `@import` processing inside comments;
|
|
* [@ben-eb](https://github.com/ben-eb) (Ben Briggs) for sharing ideas about CSS optimizations;
|
|
* [@davisjam](https://github.com/davisjam) (Jamie Davis) for disclosing ReDOS vulnerabilities;
|
|
* [@facelessuser](https://github.com/facelessuser) (Isaac) for pointing out a flaw in clean-css' stateless mode;
|
|
* [@grandrath](https://github.com/grandrath) (Martin Grandrath) for improving `minify` method source traversal in ES6;
|
|
* [@jmalonzo](https://github.com/jmalonzo) (Jan Michael Alonzo) for a patch removing node.js' old `sys` package;
|
|
* [@lukeapage](https://github.com/lukeapage) (Luke Page) for suggestions and testing the source maps feature;
|
|
Plus everyone else involved in [#125](https://github.com/jakubpawlowicz/clean-css/issues/125) for pushing it forward;
|
|
* [@madwizard-thomas](https://github.com/madwizard-thomas) for sharing ideas about `@import` inlining and URL rebasing.
|
|
* [@ngyikp](https://github.com/ngyikp) (Ng Yik Phang) for testing early clean-css 4 versions, reporting bugs, and suggesting numerous improvements.
|
|
* [@wagenet](https://github.com/wagenet) (Peter Wagenet) for suggesting improvements to `@import` inlining behavior;
|
|
* [@venemo](https://github.com/venemo) (Timur Kristóf) for an outstanding contribution of advanced property optimizer for 2.2 release;
|
|
* [@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;
|
|
* [@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.
|
|
|
|
# License
|
|
|
|
clean-css is released under the [MIT License](https://github.com/jakubpawlowicz/clean-css/blob/master/LICENSE).
|