So AVIF is a new(ish) image format that promises even better optimization then WebP and is supported in desktop Chrome & behind a preference in Firefox; go to about:config
and set image.avif.enabled
to true.
If you are using Autoptimize to optimize your images and you want to test AVIF images, you can use below code snippet to do so;
add_filter('autoptimize_filter_imgopt_webp_js', function(){return '<script data-noptimize="1">function c_img(a,b){src="avif"==b?"data:image/avif;base64,AAAAIGZ0eXBhdmlmAAAAAGF2aWZtaWYxbWlhZk1BMUIAAADybWV0YQAAAAAAAAAoaGRscgAAAAAAAAAAcGljdAAAAAAAAAAAAAAAAGxpYmF2aWYAAAAADnBpdG0AAAAAAAEAAAAeaWxvYwAAAABEAAABAAEAAAABAAABGgAAABoAAAAoaWluZgAAAAAAAQAAABppbmZlAgAAAAABAABhdjAxQ29sb3IAAAAAamlwcnAAAABLaXBjbwAAABRpc3BlAAAAAAAAAAEAAAABAAAAEHBpeGkAAAAAAwgICAAAAAxhdjFDgQ0MAAAAABNjb2xybmNseAACAAIAAYAAAAAXaXBtYQAAAAAAAAABAAEEAQKDBAAAACJtZGF0EgAKCBgADsgQEAwgMgwf8AAAWAAAAACvJ+o=":"data:image/webp;base64,UklGRhoAAABXRUJQVlA4TA0AAAAvAAAAEAcQERGIiP4HAA==";var c=new Image;c.onload=function(){var d=0<c.width&&0<c.height;a(d,b)},c.onerror=function(){a(!1,b)},c.src=src}function s_img(a,b){w=window,"avif"==b?!1==a?c_img(s_img,"webp"):w.ngImg="avif":!1==a?w.ngImg=!1:w.ngImg="webp"}c_img(s_img,"avif");document.addEventListener("lazybeforeunveil",function({target:a}){window.ngImg&&["data-src","data-srcset"].forEach(function(b){attr=a.getAttribute(b),null!==attr&&-1==attr.indexOf("/client/to_")&&a.setAttribute(b,attr.replace(/\/client\//,"/client/to_"+window.ngImg+","))})});</script>';});
Use the the code snippets plugin to add this (easy and safe) or if you’re adventurous add it to your theme’s functions.php.