# PostCSS Custom Properties [PostCSS][postcss] [![NPM Version][npm-img]][npm-url] [![CSS Standard Status][css-img]][css-url] [![Build Status][cli-img]][cli-url] [Discord][discord] [PostCSS Custom Properties] lets you use Custom Properties in CSS, following the [CSS Custom Properties] specification. [!['Can I use' table](https://caniuse.bitsofco.de/image/css-variables.png)](https://caniuse.com/#feat=css-variables) ```pcss :root { --color: red; } h1 { color: var(--color); } /* becomes */ :root { --color: red; } h1 { color: red; color: var(--color); } ``` **Note:** This plugin only processes variables that are defined in the `:root` selector. ## Usage Add [PostCSS Custom Properties] to your project: ```bash npm install postcss-custom-properties --save-dev ``` Use [PostCSS Custom Properties] as a [PostCSS] plugin: ```js const postcss = require('postcss'); const postcssCustomProperties = require('postcss-custom-properties'); postcss([ postcssCustomProperties(/* pluginOptions */) ]).process(YOUR_CSS /*, processOptions */); ``` [PostCSS Custom Properties] runs in all Node environments, with special instructions for: | [Node](INSTALL.md#node) | [PostCSS CLI](INSTALL.md#postcss-cli) | [Webpack](INSTALL.md#webpack) | [Create React App](INSTALL.md#create-react-app) | [Gulp](INSTALL.md#gulp) | [Grunt](INSTALL.md#grunt) | | --- | --- | --- | --- | --- | --- | ## Options ### preserve The `preserve` option determines whether Custom Properties and properties using custom properties should be preserved in their original form. By default, both of these are preserved. ```js postcssCustomProperties({ preserve: false }); ``` ```pcss :root { --color: red; } h1 { color: var(--color); } /* becomes */ h1 { color: red; } ``` ### importFrom The `importFrom` option specifies sources where Custom Properties can be imported from, which might be CSS, JS, and JSON files, functions, and directly passed objects. ```js postcssCustomProperties({ importFrom: 'path/to/file.css' // => :root { --color: red } }); ``` ```pcss h1 { color: var(--color); } /* becomes */ h1 { color: red; } ``` Multiple sources can be passed into this option, and they will be parsed in the order they are received. JavaScript files, JSON files, functions, and objects will need to namespace Custom Properties using the `customProperties` or `custom-properties` key. ```js postcssCustomProperties({ importFrom: [ 'path/to/file.css', // :root { --color: red; } 'and/then/this.js', // module.exports = { customProperties: { '--color': 'red' } } 'and/then/that.json', // { "custom-properties": { "--color": "red" } } { customProperties: { '--color': 'red' } }, () => { const customProperties = { '--color': 'red' }; return { customProperties }; } ] }); ``` See example imports written in [CSS](test/import-properties.css), [JS](test/import-properties.js), and [JSON](test/import-properties.json). ### overrideImportFromWithRoot The `overrideImportFromWithRoot` option determines if properties added via `importFrom` are overridden by properties that exist in `:root`. Defaults to `false`. ```js postcssCustomProperties({ overrideImportFromWithRoot: true }); ``` ### exportTo The `exportTo` option specifies destinations where Custom Properties can be exported to, which might be CSS, JS, and JSON files, functions, and directly passed objects. ```js postcssCustomProperties({ exportTo: 'path/to/file.css' // :root { --color: red; } }); ``` Multiple destinations can be passed into this option, and they will be parsed in the order they are received. JavaScript files, JSON files, and objects will need to namespace Custom Properties using the `customProperties` or `custom-properties` key. ```js const cachedObject = { customProperties: {} }; postcssCustomProperties({ exportTo: [ 'path/to/file.css', // :root { --color: red; } 'and/then/this.js', // module.exports = { customProperties: { '--color': 'red' } } 'and/then/this.mjs', // export const customProperties = { '--color': 'red' } } 'and/then/that.json', // { "custom-properties": { "--color": "red" } } 'and/then/that.scss', // $color: red; cachedObject, customProperties => { customProperties // { '--color': 'red' } } ] }); ``` See example exports written to [CSS](test/export-properties.css), [JS](test/export-properties.js), [MJS](test/export-properties.mjs), [JSON](test/export-properties.json) and [SCSS](test/export-properties.scss). ### disableDeprecationNotice Silence the deprecation notice that is printed to the console when using `importFrom` or `exportTo`. > "importFrom" and "exportTo" will be removed in a future version of postcss-custom-properties. > Check the discussion on github for more details. https://github.com/csstools/postcss-plugins/discussions/192 [cli-img]: https://github.com/csstools/postcss-plugins/actions/workflows/test.yml/badge.svg [cli-url]: https://github.com/csstools/postcss-plugins/actions/workflows/test.yml?query=workflow/test [css-img]: https://cssdb.org/images/badges/custom-properties.svg [css-url]: https://cssdb.org/#custom-properties [discord]: https://discord.gg/bUadyRwkJS [npm-img]: https://img.shields.io/npm/v/postcss-custom-properties.svg [npm-url]: https://www.npmjs.com/package/postcss-custom-properties [CSS Custom Properties]: https://www.w3.org/TR/css-variables-1/ [PostCSS]: https://github.com/postcss/postcss [PostCSS Custom Properties]: https://github.com/csstools/postcss-plugins/tree/main/plugins/postcss-custom-properties