Test methodology
What does CSS Capabilities measure?
It measures whether the browser supports a defined set of modern CSS features. It is a browser compatibility diagnostic, not a rendering-performance test.
What CSS features are checked?
The profile covers layout and components, selectors and interaction states, styling foundations, color and visual effects, typography, responsive design and motion, forms, and interface behavior.
How are CSS features tested?
The test uses CSS.supports(), selector parsing, media-query evaluation, at-rule parsing, and isolated computed-style or layout probes where syntax support alone is insufficient.
How is CSS coverage calculated?
Each of the 74 established checks has equal weight. The coverage percentage is the number of supported established features divided by 74, multiplied by 100.
Do limited-availability CSS features affect the score?
No. The 24 limited-availability checks are informational because they are not yet consistently interoperable across major browser engines.
What does 100% CSS coverage mean?
It means the browser passed every established check in the current versioned profile. It does not mean the browser supports every CSS feature ever defined.
How to interpret the result
The result reports established CSS feature coverage for the current versioned profile. Limited-availability checks are shown separately and do not affect coverage.