Detecting support for AVIF, WebP, JPEG 2000, JPEG XR and SVG to supply the best image for the UA
Download/fork the script to your server.
Insert script before any <link> tag to css file, so browser will start to download right images.
<html>
<head>
<title>My Page</title>
<script src="https://accionvegana.org/accio/0ITbvNmLiVHa0l2Z6MHc0/imgsupport.js"></script>
...
<link rel="stylesheet" href="https://accionvegana.org/accio/0ITbvNmLiVHa0l2Z6MHc0/mystyles.css">
...
Like modernizr, it injects one or a few CSS class names to the document element, e. g. <html>, according to which image formats are supported by the browser:
jxl– if browser supports JPEG XL, then this class will be added. Currently it's Chrome and Firefox behind a flag.avif– if browser supports AVIF, then this class will be added. Currently it's available on Chrome and Opera (not Edge) and in Firefox it's still behind a flag.webp– it's already in all modern browsers. But be careful Safari started to support it not that long ago and it's available only in v14+ (BigSur, iOS14+).jp2– browser supports JPEG 2000. It's Safari for Mac OS X and all browsers for iOS (based on iOS WebKit).jpx– browser supports JPEG XR... Internet Explorer 9+ and old MS Edge till v18.svg– all modern browsers, but this class is set only if none of the above formats are supported. Currently it's Firefox only.png– if even SVG is not supported... fallback variant.- Additionally are added classes if the format is not supported:
notjxl,notavif,notwebp,notjp2,notjpxandnotsvg.
Chrome
<html class="notjxl avif webp notjpx notjp2">
Safari
<html class="notjxl notavif webp notjpx jp2">
Firefox
<html class="notjxl notavif webp notjpx notjp2 svg">
You can use css-cascade to specify what kind of image your browser must download:
.jxl .myelem {
background-image: url('myimage.jxl');
}
.avif.notjxl.notwebp .myelem {
background-image: url('myimage.avif');
}
.webp.notjxl.notavif .myelem {
background-image: url('myimage.webp');
}
.jpx.notavif.notwebp .myelem {
background-image: url('myimage.wdp');
}
.jp2.notavif.notwebp .myelem {
background-image: url('myimage.jp2');
}
.svg .myelem {
background-image: url('myimage.svg');
}
.png .myelem {
background-image: url('myimage.png');
}