PleaseHTML5 features you can finally drop the polyfill for in 2026
When HTML5 Please first launched, half the job was working out which shiny new feature needed a polyfill, which needed a prefix, and which you should avoid until Internet Explorer caught up. More than a decade later, most of that scaffolding is dead weight. Here are the features you can use with a clear conscience, and the old workarounds you can finally remove.
Rounded corners, shadows and opacity
border-radius, box-shadow and opacity were once prefixed and patchy. Today they are baseline in every browser people actually use. Delete the vendor prefixes, delete the curved corner image hacks, and style directly.
Layout that just works
Flexbox and CSS Grid ended the era of float based layouts and clearfix hacks. If your reset still ships an inline block grid system, that is a good afternoon of cleanup. Pair them with box-sizing: border-box, which belongs near the top of every stylesheet.
Media and graphics
canvas, audio and video no longer need Flash fallbacks. The Geolocation API and WebGL are broadly supported too, though WebGL performance still varies by device, so keep a fallback path for the heaviest scenes.
What to still be careful with
Not everything aged into safety. CSS Regions, Exclusions and scoped styles never made it and should be avoided. Browse the full picture in the CSS, HTML and JavaScript API sections, and when in doubt the Can I Use link on every feature page shows the live numbers.
The rule of thumb
The safest test is still the one HTML5 Please was built around: check the recommendation, check the support, and enhance progressively so the experience holds up when a feature is missing. The difference in 2026 is that the list of things you need to worry about is a lot shorter. Start on the feature finder.