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Regex tester

Match highlighting, groups, replace and flags, run in a worker with a timeout.

Runs in your browser; nothing is uploaded

Use i, m, s or u once each. Global matching is always on.

Runs in a browser worker with a 500 ms deadline. Text stops at 100,000 characters; results stop at 1,000 matches. Nothing is uploaded.

Test and replace patterns

Regex tester reports global match positions, numbered and named capture groups, and optional replacement output. It supports JavaScript i, m, s and u flags. Zero-length matches advance safely and results stop at 1,000 rows.

Bounded execution and privacy

A pattern can take a long time on certain text. This tool runs it in a separate browser worker and terminates the worker after 500 ms or when you cancel. Pattern, text and replacement are never uploaded or kept in the URL. A timeout means the result is incomplete, not that the pattern is invalid.

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