Flag Checks

Paste a FastFlag list and have it validated against all 24,086 known flags. Accepts JSON or a plain list of names.

Existence check

Catch typos and made-up flags. A name that doesn't exist is silently ignored by the client, so it's easy to miss.

Open

Duplicate check

Find flags listed more than once, and flag the cases where the repeats disagree on a value.

Open

Stability check

See which flags fall outside the curated set — real, but untested and more likely to misbehave.

Open

Nothing you paste is stored — checks run against the flag index and the result is returned straight back to your browser.