What is Regex Tester?
Regex Tester lets you build and debug JavaScript regular expressions interactively. Matches highlight as you type, with group breakdowns and flag toggles.
How to use
- Type a pattern (without the slashes) and toggle flags.
- Paste a test string below.
- Inspect matches and capture groups on the right.
Frequently asked questions
What regex flavor does it use?
JavaScript (ECMAScript) regex via the native RegExp engine.
Is it safe against catastrophic backtracking?
Yes — each evaluation runs with a 1s timeout and input length cap to prevent ReDoS.
Can I share a pattern?
URL sharing is on the roadmap; for now copy/paste both pattern and flags.