Web features for a self-contained HTML file

Every feature in the web-features dataset, sorted by whether it works in one HTML file with inline CSS and JS, loaded from file:// or any web host, with no network, in current Chrome, Firefox and Safari. Baseline status and browser versions come from the dataset; the offline verdicts are hand-curated and should be read as claims to test, not facts.

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How the verdicts were made

Start from Baseline "widely available" (supported in every core browser for 30+ months). Then subtract anything that needs a network or server, a real (non-opaque) origin, an HTTP header, or a permission prompt — none of which a file opened from disk can provide. What's left is Always available. Available with caveats means it works everywhere but with a file://-specific constraint (for example, workers must be created from a blob: URL because Chromium gives every local file its own opaque origin). Each verdict shows whether it came from a per-feature override or a group rule; open a row to read the reason.

The dataset is fetched from jsDelivr (pinned to web-features v3.x, so the schema cannot change underneath this page) with unpkg as a fallback, then reduced to the fields shown here and kept in localStorage. After the first successful load the page works offline; on later visits it renders the local copy immediately and checks for a newer release in the background. Append src=https://…/ to the URL hash to point it at a different mirror.

Two known limitations: the dataset does not model file://, so a verdict of "Always available" for a feature with no override is a default, not a checked claim; and "Newly available" features are shown with the same verdicts so you can see what will join the list once they pass 30 months. Use the date floor to match an older browser cohort.

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