Regex Tester

Test JavaScript regex, capture groups, and replacements in an isolated Worker

All input is processed in this browser and is never sent to a server or written to local storage.

Matches

Positions use UTF-16 indexes

REGEXP

JavaScript engine

Uses the browser-native RegExp; supports d, g, i, m, s, u, v, and y flags when available.

Isolated and cancellable

Each run uses a separate Worker. Stopping, editing, or leaving terminates the current job.

Bounded match cards

At most 1,000 matches are displayed; replacement preview still runs over the complete expression.