Developer

Regex Tester

Debug regex patterns privately in your browser. Processing stays on your device — no upload, no account.

How to use Regex Tester

  1. Enter a pattern and optional flags.
  2. Paste sample text.
  3. Review matches and indices.

Why use this free regex tester tool?

  • All processing happens locally in your browser. Your files are never uploaded to a server.
  • Flags: g i m s u y.
  • Match list with indices.
  • Invalid pattern errors surfaced.

Technical details

Uses the JS RegExp engine in your browser. Catastrophic backtracking can freeze the tab on pathological patterns - keep tests small.

Regex Tester FAQ

Is input uploaded?

No. All processing happens locally in your browser. Your files are never uploaded to a server.

Which flavor?

JavaScript RegExp (ECMAScript), not PCRE/Python.

Named groups?

Shown when your browser supports them.

Tab froze?

Simplify the pattern - some regexes are exponential on certain inputs.

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