Check CSS property and JavaScript API browser compatibility with Can I Use data and polyfill suggestions.
A feature name is the unit of inquiry here: enter a CSS property or JavaScript API to see its recorded support across browser versions, based on Can I Use compatibility data. When a gap can be addressed, the result may also point to a polyfill. The important surprise is that a browser marked as supporting a feature has not necessarily implemented every subfeature or behavior. Partial-support notes and the precise feature entry matter more than a simple supported or unsupported label.
A query selects a web-platform feature represented in Can I Use data. The checker reports that feature's compatibility statuses by browser and version, answering a version-level support question. It does not analyze an application, inspect bundled code, validate syntax, or prove that a particular declaration or API call behaves correctly.
Any polyfill suggestion should be considered separately from native compatibility. A polyfill can supply or approximate an unavailable JavaScript API, but it does not change the browser's native support status. For CSS features and platform behavior, a practical equivalent may not exist, so the absence of a suggestion does not necessarily indicate a failed lookup.
No. It reports compatibility associated with browser families and versions in its data source; it is not a runtime feature test for the current visitor. For code that must adapt at execution time, use feature detection appropriate to the API or CSS construct, and retain a fallback where nominal support may be incomplete.
No. A suggestion identifies a possible compatibility aid, not full equivalence to a native implementation. Review what the polyfill covers, its browser constraints, payload cost, licensing, and unsupported semantics. CSS rendering behavior, permissions, hardware-backed capabilities, and security-sensitive APIs may be impossible or inappropriate to reproduce with a polyfill.
The behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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