minify-html-css

minify-html-css

🔽 A JavaScript (TypeScript) library to minify HTML and CSS.

Table of Contents

• Intent
• Features
• Installation
• Usage
• API Documentation
• TODO
• Contributing
• License
• Acknowledgements

Intent

I created this project to bring together the most performant HTML and CSS minifier libraries (according to my tests and findings) as clean, easy-to-use functions with well-documented options. The goal is to make web minification accessible, fast, and developer-friendly.

Features

• Minifies HTML strings
• Removes unnecessary whitespace and comments
• Works seamlessly in Node.js and browser environments
• Written in TypeScript with type definitions included

Installation

npm install minify-html-css

Usage

Basic Example

import { minifyHTML } from 'minify-html-css';

const html = `
  <div>
    <!-- This is a comment -->
    <h1> Hello World! </h1>
    <style>
      body { color: red; }
    </style>
  </div>
`;

const minifiedHtml = minifyHTML(html).code;
console.log(minifiedHtml); // "<div><h1>Hello World!</h1><style>body{color:red}</style></div>"

API Documentation

minifyHTML(input: string, options?: MinifyHTMLOptions): TransformOutput

Description: Minifies an HTML string by removing unnecessary whitespace, comments, and compressing inline JS and CSS (where supported). Returns an object containing code property for transformed code and errors array for possible errors.

Implementation note: This function is a wrapper around the @swc/html package and uses its minification logic under the hood.

Parameters:

• input (string): The HTML code to minify.
• options? (MinifyHTMLOptions): Configuration object for fine-grained control.

The available options are:

Option	Type	Default	Description
collapseWhitespaces	'none' | 'all' | 'smart' | 'conservative' | 'advanced-conservative' | 'only-metadata'	'all'	Controls how whitespace is collapsed and removed throughout the document.
removeEmptyMetadataElements	boolean	true	Removes empty metadata elements such as <script>, <style>, <meta>, and <link>.
removeComments	boolean	true	Removes all HTML comments unless matched by preserveComments.
preserveComments	string[]		Array of regex strings; comments matching any are preserved. You can override the default patterns.
minifyConditionalComments	boolean	true	Minifies IE conditional comments.
removeEmptyAttributes	boolean	true	Removes empty attributes from HTML tags (when safe).
removeRedundantAttributes	'none' | 'all' | 'smart'	'smart'	Controls removal of redundant or default attributes.
collapseBooleanAttributes	boolean	true	Collapses boolean attributes to their short form (e.g. checked).
normalizeAttributes	boolean	true	Cleans up attribute values by removing unnecessary spaces, and strips javascript: from event handlers.
minifyJson	boolean | { pretty?: boolean }	true	Minifies embedded JSON within <script type="application/json">.
minifyJs	boolean	true	Minifies inline JavaScript.
minifyCss	boolean	true	Minifies inline CSS.
minifyAdditionalScriptsContent	[string, MinifierType][]		Minifies additional <script> types, specifying type pattern and minifier.
minifyAdditionalAttributes	[string, MinifierType][]		Minifies additional attribute values, specifying attribute name pattern and minifier.
sortSpaceSeparatedAttributeValues	boolean	false	Sorts space-separated attribute values like class or rel.
sortAttributes	boolean	false	Sorts all attributes of each element in reverse alphabetical order.
tagOmission	boolean	true	Omits optional end tags when valid per HTML spec.
quotes	boolean	false	Always wrap attribute values in quotes.

For detailed type definitions and documentation, see src/minify-html-types.ts.

TODO

• Implement CSS minification function (minifyCSS) built on top of Lightning CSS
• Implement CLI usage (command-line tool)

Contributing

We welcome contributions!

Requirements:

• Bun (make sure you have Bun installed)

Steps:

• Fork this repository.
• Create a new branch: git switch -c my-feature
• Make your changes and add tests if possible.
• Run bun run lint && bun test (This is automatically done when you open a pull request) to ensure everything passes.
• Commit your changes: git commit -m "Add my feature"
• Push to your fork and submit a pull request.

Please read our CONTRIBUTING.md for more details.

License

This project is licensed under the MIT License.

Types License Notice:

• The type definitions in src/minify-html-types.ts are adapted from the SWC Project and are licensed under the Apache License, Version 2.0.
• See the NOTICE file and LICENSE-APACHE for more information and required attributions.

Acknowledgements

• This project uses @swc/html under the hood for actual HTML minification.
  We adapt and update their type definitions, add documentation, and keep their license and notice files in the repository for compliance and transparency. See the repository for more information.