Regex Tester

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

• 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.