# LightningCSS — Ultra-Fast CSS Parser, Transformer, and Minifier

> An extremely fast CSS parser, transformer, bundler, and minifier written in Rust, with built-in support for CSS Modules, nesting, and vendor prefixing.

## Install

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# LightningCSS — Ultra-Fast CSS Parser, Transformer, and Minifier

## Quick Use
```bash
# Install the CLI
npm install -g lightningcss-cli
# Minify and transform a CSS file
lightningcss --minify --targets '>= 0.25%' input.css -o output.css
```

## Introduction
LightningCSS (formerly Parcel CSS) is a CSS parser, transformer, bundler, and minifier written in Rust. It is designed to be orders of magnitude faster than JavaScript-based CSS tools while providing modern features like automatic vendor prefixing, syntax lowering, and CSS Modules support out of the box.

## What LightningCSS Does
- Parses CSS into a typed AST with full spec compliance and error recovery
- Minifies CSS with advanced optimizations including shorthand merging and color conversion
- Automatically adds or removes vendor prefixes based on browser targets
- Lowers modern CSS syntax (nesting, color functions, custom media queries) for older browsers
- Supports CSS Modules with scoped class names and composition

## Architecture Overview
LightningCSS is built as a Rust library with bindings for Node.js (via NAPI-RS) and a standalone CLI. The parser produces a strongly-typed AST that preserves source maps. Transformations operate on this AST in a single pass where possible, applying browser target lowering, vendor prefixing, and minification together. The minifier performs structural optimizations like merging adjacent rules, collapsing shorthand properties, and converting color formats.

## Self-Hosting & Configuration
- Install the CLI via npm or download prebuilt binaries from GitHub releases
- Use as a library in Node.js via the lightningcss npm package
- Integrate with bundlers: native Parcel support, community plugins for Vite and Webpack
- Configure browser targets using browserslist syntax for automatic prefix and lowering decisions
- Enable CSS Modules, custom at-rules, or draft specs via API options

## Key Features
- 100x+ faster than cssnano and autoprefixer combined in benchmarks
- Typed AST means transformations are safe and spec-correct
- Built-in CSS Modules with composesFrom and scoped naming
- Handles modern CSS features: nesting, :is(), color-mix(), light-dark(), and more
- Preserves source maps through all transformations

## Comparison with Similar Tools
- **PostCSS + Autoprefixer** — plugin-based JS pipeline; LightningCSS is a single Rust binary, far faster
- **cssnano** — JS minifier; LightningCSS minifies more aggressively and runs 100x faster
- **esbuild CSS** — fast but less complete CSS handling; LightningCSS has deeper CSS spec support
- **Tailwind CSS compiler** — utility-class generator; LightningCSS processes standard CSS files
- **sass/less** — preprocessors with custom syntax; LightningCSS works with standard CSS and modern specs

## FAQ
**Q: Can LightningCSS replace PostCSS in my build pipeline?**
A: For most use cases (prefixing, nesting, minification), yes. If you rely on PostCSS plugins with custom transforms, you may still need PostCSS for those.

**Q: Does it support Sass or Less syntax?**
A: No. LightningCSS processes standard CSS. You would run Sass/Less compilation first, then LightningCSS.

**Q: How do I use it with Vite?**
A: Vite has experimental built-in support for LightningCSS as its CSS transformer via the css.transformer option.

**Q: Is the AST API stable for building custom tools?**
A: The Rust API is well-documented and versioned. The Node.js API mirrors the Rust API with JavaScript-friendly types.

## Sources
- https://github.com/parcel-bundler/lightningcss
- https://lightningcss.dev

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Source: https://tokrepo.com/en/workflows/asset-29c758c9
Author: AI Open Source