Unplugin-inject-preload NPM

unplugin-inject-preload

This plugin adds preload links by getting output assets from the build tools you are using.

Supporting:

Vite 4 and 5 (on build only)
Webpack 5 (with HtmlWebpackPlugin 5)
Rspack (with HtmlWebpackPlugin 5 or HtmlRspackPlugin)

!NOTE This plugin combines vite-plugin-inject-preload and html-webpack-inject-preload into one package.
See the migration guide for vite-plugin-inject-preload and html-webpack-inject-preload .

Install

#npm
npm i -D unplugin-inject-preload
#yarn
yarn add -D unplugin-inject-preload
#pnpm
pnpm i -D unplugin-inject-preload

// vite.config.ts
import UnpluginInjectPreload from 'unplugin-inject-preload/vite'

export default defineConfig({
  plugins: [
    UnpluginInjectPreload({ /* options */ }),
  ],
})

Example: playground/vitejs

The Vite plugin only works on build because of the way Vite behave.

// webpack.config.js
const HtmlWebpackPlugin = require('html-webpack-plugin')
const UnpluginInjectPreload = require('unplugin-inject-preload/webpack')

module.exports = {
  plugins: [
    HtmlWebpackPlugin({ /*  HtmlWebpackPlugin options */ }),
    UnpluginInjectPreload({ /* options */ }),
  ]
}

Example: playground/webpack

// rspack.config.js
const HtmlWebpackPlugin = require('html-webpack-plugin')
const UnpluginInjectPreload = require('unplugin-inject-preload/rspack')

module.exports = {
  plugins: [
    HtmlWebpackPlugin({ /*  HtmlWebpackPlugin options */ }),
    UnpluginInjectPreload({ /* options */ }),
  ]
}

Example: playground/rspack

// rspack.config.js
const HtmlWebpackPlugin = require('html-webpack-plugin')
const UnpluginInjectPreload = require('unplugin-inject-preload/rspack')

module.exports = {
  plugins: [
    new rspack.HtmlRspackPlugin({ /* HtmlRspackPlugin options */ }),
    UnpluginInjectPreload({ /* options */ }),
  ]
}

Example: playground/rspack

👨‍💻 Usage

All example are presented for ViteJS but this is the same behavior for Webpack and RsPack

All the files needs to be process by the bundler to be find by the plugin. For example, if I load this CSS file :

@font-face {
  font-family: 'Roboto';
  src: url('./../fonts/Roboto-Italic.woff2');
  font-weight: 400;
  font-style: italic;
}

@font-face {
  font-family: 'Roboto';
  src: url('./../fonts/Roboto-Regular.woff2');
  font-weight: 400;
  font-style: normal;
}

I can make the following configuration for UnpluginInjectPreload :

// vite.config.js / vite.config.ts
import UnpluginInjectPreload from 'unplugin-inject-preload/vite'

export default {
  plugins: [
    UnpluginInjectPreload({
      files: [
        {
          entryMatch: /Roboto-[a-zA-Z]*\.woff2$/,
        },
        {
          outputMatch: /lazy.[a-z-0-9]*.(css|js)$/,
        }
      ]
    })
  ]
}

Options

files: An array of files object
- entryMatch: A regular expression to target entry files you want to preload
- outputMatch: A regular expression to target output build files you want to preload
  You need to set at least entryMatch or/and outputMatch. Be aware that entry file is not always present for webpack and entryMatch will do nothing.
- attributes (optional): If this option is ommited, it will determine the mime and the as attributes automatically. You can also add/override any attributes you want.
injectTo (optional): By default, the preload links are injected with the 'head-prepend' options. But you can pass 'head' to inject preload links at bottom of the head tag if you need it. You can pass the 'custom' option and put  in your .html file where you want to inject the preload links.

With the full options usage, you can do something like this :

// vite.config.js / vite.config.ts
import UnpluginInjectPreload from 'unplugin-inject-preload/vite'

export default {
  plugins: [
    UnpluginInjectPreload({
      files: [
        {
          entryMatch: /Roboto-[a-zA-Z]*\.woff2$/,
          outputMatch: /Roboto-[a-zA-Z]*-[a-z-0-9]*\.woff2$/,
          attributes: {
            'type': 'font/woff2',
            'as': 'font',
            'crossorigin': 'anonymous',
            'data-font': 'Roboto'
          }
        },
        {
          outputMatch: /lazy.[a-z-0-9]*.(js)$/,
          attributes: {
            rel: 'modulepreload',
            type: undefined,
          }
        }
      ],
      injectTo: 'head-prepend'
    })
  ]
}

Migration

From vite-plugin-inject-preload

package.json

{
  "devDependencies": {
-   "vite-plugin-inject-preload": "*",
+   "unplugin-inject-preload": "^2.0.0",
  }
}

vite.config.js

- import VitePluginInjectPreload from 'vite-plugin-inject-preload'
+ import UnpluginInjectPreload from 'unplugin-inject-preload/vite'

export default {
  plugins: [
    VitePluginInjectPreload({
      files: [
        {
-         match: /Roboto-[a-zA-Z]*-[a-z-0-9]*\.woff2$/,
+         outputMatch: /Roboto-[a-zA-Z]*-[a-z-0-9]*\.woff2$/,
          attributes: {
            'type': 'font/woff2',
            'as': 'font',
            'crossorigin': 'anonymous',
            'data-font': 'Roboto'
          }
        },
      ],
      injectTo: 'head-prepend'
    })
  ]
}

From html-webpack-inject-preload

package.json

{
  "devDependencies": {
-   "@principalstudio/html-webpack-inject-preload": "*",
+   "unplugin-inject-preload": "^2.0.0",
  }
}

const HtmlWebpackPlugin = require('html-webpack-plugin');
- const HtmlWebpackInjectPreload = require('@principalstudio/html-webpack-inject-preload');
+ const UnpluginInjectPreload = require('unplugin-inject-preload/webpack');

module.exports = {
  entry: 'index.js',
  output: {
    path: __dirname + '/dist',
    filename: 'index_bundle.js'
  },
  plugins: [
    new HtmlWebpackPlugin(),
-   new HtmlWebpackInjectPreload({
+   UnpluginInjectPreload({
      files: [
        {
-         match: /.*\.woff2$/,
+         outputMatch: /.*\.woff2$/,
          attributes: {
            as: 'font',
            type: 'font/woff2', crossorigin: true
          },
        },
      ]
    })
  ]
}