Awesome

AVIF in CSS

PostCSS plugin and a tiny JS script (315B gzipped) to use the AVIF image format for CSS background images.

Use AVIF in Supported Browsers and fall back to the original image in other browsers.

Take a look at the demo site avif-in-css.netlify.app

About AVIF

AVIF offers significant compression gains vs. JPEG and WebP, with a recent Netflix study showing 50% savings vs. standard JPEG and > 60% savings on 4:4:4 content

How works?

You add require('avif-in-css') to your JS bundle and write CSS like:

.logo {
  width: 80px;
  height: 80px;
  background-image: url(logo.jpg);
}

The script will set avif or no-avif class on <body> and PostCSS plugin will generate:

.logo {
  width: 80px;
  height: 80px;
}
body.avif .logo {
  background-image: url(logo.avif);
}
body.no-avif .logo {
  background-image: url(logo.jpg);
}

Usage

1. Convert to AVIF

Convert you images to AVIF format, you can use Squoosh, Avif.app, Convertio.co, avif.io or any other tool. Important: This PostCSS plugin doesn't convert the images to AVIF format.

2. Install `avif-in-css`

npm install --save-dev avif-in-css

2.1 Load the polyfill

Add the JS script to your client-side JS bundle:

// CommonJS
+ require('avif-in-css/polyfill.js')

// ES6
+ import 'avif-in-css/polyfill.js'

Since JS script is very small (315B gzipped), the best way for landings is to inline it to HTML:

+   <script><%= readFile('node_modules/AVIF-in-css') %></script>
  </head>

You can load the script via CDN:

+   <script src="https://unpkg.com/avif-in-css/polyfill.js"></script>
  </head>

2.2 Load the PostCSS plugin

Check do you use PostCSS already in your bundler. You can check postcss.config.js in the project root, "postcss" section in package.json or postcss in bundle config.

If you don’t have it already, add PostCSS to your bundle:

For webpack see postcss-loader docs.
For Parcel create postcss.config.js file. It already has PostCSS support.

Add `avif-in-css` to PostCSS plugins

module.exports = {
  plugins: [
+   require('avif-in-css'),
    require('autoprefixer')
  ]
}

If you use CSS Modules in webpack add modules: true option:

module.exports = {
  plugins: [
-   require(avif-in-css'),
+   require(avif-in-css')({ modules: true }),
    require('autoprefixer')
  ]
}

PostCSS Options

module.exports = {
  plugins: [
    require('avif-in-css')({ /* options */ }),
  ]
}

Option	Description	Default Value	Type Value
`modules`	Wrap classes to `:global()` to support CSS Modules.	`false`	Boolean
`avifClass`	Class name for browser with AVIF support.	`avif`	String
`noAvifClass`	Class name for browser without AVIF support.	`no-avif`	String
`rename`	Get a new file name from old name, like `(oldName: string) => string`, then `url(./image.png)` → `url(./image.png.avif)`.		Function

Supported browsers

Chrome Desktop 85+
Firefox 63+ (with media.av1.enabled activated)
Firefox for Android 64+ (with media.av1.enabled and media.av1.use-dav1d activated)
Edge 18+ (with AV1 Video Extension installed)