OomTools

JavaScript Regex Tester

Build and try out JavaScript regular expressions against your own sample text, with matches highlighted live, capture groups broken out, and flags for case-insensitive, multiline and dotall matching. It all runs in your browser, so your patterns and test data stay private.

  • 100% free
  • Private & safe
  • Runs in your browser

Why use Regex Tester?

Regex Tester is a quick, no-nonsense developer utility that runs entirely client-side, so your code and data never leave your machine.

  • Runs instantly in your browser — nothing to install, nothing uploaded.
  • Completely free, with no account, no watermarks and no usage limits.
  • Handles JavaScript RegExp syntax; Flags: g (always on), i, m, s.
  • Enter a pattern and choose flags (i, m, s).
  • Works on any device — desktop, tablet and phone — and is fully keyboard accessible.

How to use Regex Tester

  1. Enter a pattern and choose flags (i, m, s).
  2. Type or paste your test string.
  3. See matches highlighted live, with a table of indexes and capture groups.
  4. Refine the pattern until it matches what you need.

Examples

  • Testing an email pattern against sample text.
  • Checking capture groups for a date format.

Supported formats & limits

  • JavaScript RegExp syntax
  • Flags: g (always on), i, m, s

Limitations

  • Uses JavaScript's regex engine, which differs from PCRE/Python in some features.
  • The global flag is always applied to find all matches.
  • Catastrophic patterns are guarded but can still be slow.

Frequently asked questions

Which regex flavor is this?

JavaScript's built-in engine, so syntax matches what runs in browsers and Node.

Are capture groups shown?

Yes, both numbered and named groups appear in the results table.

Is my pattern uploaded?

No — everything runs in your browser.

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