Regex Tester

Test a regular expression instantly

Enter a pattern, choose your flags, paste some test text, and this tool shows every match with its position and capture groups. It uses the browser's native JavaScript regex engine, so what you see here is exactly how the pattern behaves in RegExp, Node.js and the browser. Nothing is sent anywhere — test freely with real data.

Flags you can use

• g — global: find all matches, not just the first.
• i — case-insensitive.
• m — multiline: ^ and $ match line starts/ends.
• s — dotall: . also matches newlines.
• u — unicode; y — sticky.

The tester always searches globally so you can see every match, then lists each one with its index and the contents of any capture groups.

Capture groups and named groups

Parentheses create capture groups you can reference later. (\w+)@(\w+) captures the parts before and after an @. Named groups — (?<user>\w+) — make patterns self-documenting and let you pull values out by name. This tester displays both numbered and named groups for every match, which is the fastest way to confirm your groups capture what you intend.

Tips for writing reliable patterns

• Anchor with ^ and $ when you mean to match a whole string.
• Prefer specific character classes ([a-z]) over a broad ..
• Watch out for "catastrophic backtracking" with nested quantifiers like (a+)+ on long inputs.
• Escape special characters (. * + ? ( ) [ ] \) when you mean them literally.

Where it fits

Once your pattern works here, drop it straight into your code. Validating structured text? You might also want the JSON formatter or the URL encoder for the surrounding pipeline.