@parcel/css

A CSS parser, transformer, and minifier written in Rust.

Features

Documentation

@parcel/css can be used from Parcel, as a standalone library from JavaScript or Rust, using a standalone CLI, or wrapped as a plugin within any other tool.

From Node

See the TypeScript definitions for full API docs.

Here is a simple example that compiles the input CSS for Safari 13.2, and minifies the output.

```js const css = require('@parcel/css');

let {code, map} = css.transform({ filename: 'style.css', code: Buffer.from('.foo { color: red }'), minify: true, sourceMap: true, targets: { // Semver versions are represented using a single 24-bit number, with one component per byte. // e.g. to represent 13.2.0, the following could be used. safari: (13 << 16) | (2 << 8) } }); ```

You can also convert the results of running browserslist into targets which can be passed to @parcel/css:

```js const browserslist = require('browserslist'); const css = require('@parcel/css');

let targets = css.browserslistToTargets(browserslist('>= 0.25%')); ```

Bundling is also possible by using the bundle API. This processes @import rules and inlines them. This API requires filesystem access, so it does not accept code directly via the API.

js let {code, map} = css.bundle({ filename: 'style.css', minify: true });

From Rust

See the Rust API docs on docs.rs. More docs and examples are coming soon. For now, start with the StyleSheet API.

With Parcel

Add the following to your .parcelrc:

json { "extends": "@parcel/config-default", "transformers": { "*.css": ["@parcel/transformer-css-experimental"] }, "optimizers": { "*.css": ["@parcel/optimizer-css"] } }

You should also add a browserslist property to your package.json, which defines the target browsers that your CSS will be compiled for.

While Parcel CSS handles the most commonly used PostCSS plugins like autoprefixer, postcss-preset-env, and CSS modules, you may still need PostCSS for more custom plugins like TailwindCSS. If that's the case, just add @parcel/transformer-postcss before @parcel/transformer-css-experimental, and your PostCSS config will be picked up automatically. You can remove the plugins listed above from your PostCSS config, and they'll be handled by Parcel CSS.

You can also configure Parcel CSS in the package.json in the root of your project. Currently, three options are supported: drafts, which can be used to enable CSS nesting and custom media queries, pseudoClasses, which allows replacing some pseudo classes like :focus-visible with normal classes that can be applied via JavaScript (e.g. polyfills), and cssModules, which enables CSS modules globally rather than only for files ending in .module.css.

json { "@parcel/transformer-css": { "cssModules": true, "drafts": { "nesting": true, "customMedia": true }, "pseudoClasses": { "focusVisible": "focus-ring" } } }

From Deno or in browser

The @parcel/css-wasm package can be used in Deno or directly in browsers. This uses a WebAssembly build of Parcel CSS. Use TextEncoder and TextDecoder convert code from a string to a typed array and back.

```js import init, {transform} from 'https://unpkg.com/@parcel/css-wasm';

await init();

let {code, map} = transform({ filename: 'style.css', code: new TextEncoder().encode('.foo { color: red }'), minify: true, });

console.log(new TextDecoder().decode(code)); ```

With webpack

css-minimizer-webpack-plugin has builtin support for @parcel/css. Install @parcel/css in your project, and configure the plugin as documented here.

From the CLI

Parcel CSS includes a standalone CLI that can be used to compile, minify, and bundle CSS files. It can be used when you only need to compile CSS, and don't need more advanced functionality from a larger build tool such as code splitting and support for other languages.

To use the CLI, install the @parcel/css-cli package with an npm compatible package manager:

shell npm install @parcel/css-cli

Then, you can run the parcel-css command via npx, yarn, or by setting up a script in your package.json.

json { "scripts": { "build": "parcel-css --minify --nesting --bundle --targets '>= 0.25%' --sourcemap input.css -o output.css" } }

To see all of the available options, use the --help argument:

shell npx parcel-css --help

Benchmarks

image image

``` $ node bench.js bootstrap-4.css cssnano: 544.809ms 159636 bytes

esbuild: 17.199ms 160332 bytes

parcel-css: 4.16ms 143091 bytes

$ node bench.js animate.css cssnano: 283.105ms 71723 bytes

esbuild: 11.858ms 72183 bytes

parcel-css: 1.973ms 23666 bytes

$ node bench.js tailwind.css cssnano: 2.198s 1925626 bytes

esbuild: 107.668ms 1961642 bytes

parcel-css: 43.368ms 1824130 bytes ```