HTML Critical Webpack Plugin

This plugin extracts critical CSS and runs after all files have been emitted so you can use it after Mini CSS Extract Plugin and HTML Webpack Plugin.

Check out the demo or read the blog post Critical CSS and Webpack: Automatically Minimize Render-Blocking CSS for more details on usage.

Installation

npm i --save-dev html-critical-webpack-plugin

Note: As critical itself has a dependency on puppeteer in order to run Headless Chrome, consumers of this plugin will need to make sure that their build environment (local, CI, etc) where they are running Webpack with this plugin has the necessary operating system packages installed. See this page for more information on troubleshooting puppeteer.

Example

...

const HtmlCriticalWebpackPlugin = require("html-critical-webpack-plugin");

module.exports = {
  mode: 'production',
  plugins: [
    new HtmlWebpackPlugin({ ... }),
    new MiniCssExtractPlugin({ ... }),
    new HtmlCriticalWebpackPlugin({
      base: path.resolve(__dirname, 'dist'),
      src: 'index.html',
      dest: 'index.html',
      inline: true,
      minify: true,
      extract: true,
      width: 375,
      height: 565,
      penthouse: {
        blockJSRequests: false,
      }
    })
  ]
  ...
};

Note: Order is import here since critical, the underlying package used by this plugin, only operates against the file system, and not against webpack's build time compilation. The order of operations by critical is as such:

1. Reads the file from disk as defined by the src option
2. Extracts the CSS from that file that is deemed as "critical"
3. Writes the new file back to disk with that critical CSS inlined, at the location of the dest option

Development

Local environment

Since the main dependency of this project, critical, depends on an environment that supports Headless Chrome, Docker has been provided to support local development of this project.

After you have installed Docker, you can do the following to get setup:

1. Start the container - docker-compose up -d
2. SSH into the container - docker exec -it html-critical-webpack-plugin_nodejs_1 /bin/bash
3. Install dependencies - rm -rf node_modules && npm install (this ensures Linux specific dependencies get installed)

Now you can run the project's npm scripts like usuual:

1. Run unit tests - npm run test
2. Run the build - npm run ci

Note: changes are bi-directional

Learn more about Docker here or configuring Headless Chrome for your own machine.

Workflows

1. To run unit tests - npm run test
2. To build the project - npm run ci
3. To build the project for release - npm run build