Regex Tester

Build and debug regular expressions against real text, with every match highlighted as you type. It uses your browser's native JavaScript regex engine, so what you see here is exactly what RegExp will do in your code.

Flags

Toggle the standard flags, each with a tooltip:

• g — global: find every match, not just the first.
• i — ignore case.
• m — multiline: ^ and $ match at line breaks.
• s — dotall: . also matches newlines.
• u — unicode mode.
• y — sticky: match only at the current position.

Matches and groups

Every match is highlighted in the test text and listed below with its capture groups. Named groups like (?<year>\d{4}) are captured too. An invalid pattern shows a clear error instead of failing silently.

Privacy and safety

Your pattern and test text run entirely in your browser — nothing is uploaded. Because it uses the native engine, evaluation is instant, and a safety cap prevents pathological patterns from freezing the page.