Why does :has() still show unsupported?

Some browsers gate it behind flags or block it in compatibility modes. Update to the latest stable or disable compatibility view.

Does flex gap work in my version of Safari?

Flex gap landed in Safari 14.1+. Older iOS/Safari releases need margin-based spacing instead.

Can a missing feature be polyfilled?

Layout features are hard to polyfill reliably. Where possible, update the browser; otherwise provide fallback CSS in your app.

Browser Diagnostics

CSS Feature Test

Layout and visual feature detection

CSS Feature Support

Modern layout and visual features

0/0 supported

Diagnose layout breakages

Modern sites depend on Grid, Flexbox gap, sticky, and :has() selectors for layout. If any of these fail, you may see overlapping cards, stuck headers, or filters that don’t apply. Use this test to match what the site expects.

Older Chromium forks or enterprise policies can disable experimental selectors like :has(). Safari before 17 also lacked :has(); upgrade if you need advanced form or card layouts.

Seeing blurred/transparent UI fail?

backdrop-filter requires GPU-accelerated compositing. Ensure hardware acceleration is on and try the WebGL test as well.

Run WebGL Test Hardware acceleration

Fix common CSS breakages

If layouts look broken or styles don’t apply, start with a browser update, then check for extensions or compatibility modes that override CSS.

Fix CSS not working →Update browser Blurry text / zoom issues

FAQ

Why does :has() still show unsupported?: Some browsers gate it behind flags or block it in compatibility modes. Update to the latest stable or disable compatibility view.
Does flex gap work in my version of Safari?: Flex gap landed in Safari 14.1+. Older iOS/Safari releases need margin-based spacing instead.
Can a missing feature be polyfilled?: Layout features are hard to polyfill reliably. Where possible, update the browser; otherwise provide fallback CSS in your app.