Regex Tester

See what your pattern actually matches

Regular expressions are famously write-once, debug-forever. The fastest way to understand one is to watch it run: type a pattern and this tool highlights every match in your test string live, lists each match with its position, and breaks out numbered and named capture groups. Toggle the flags — g global, i case-insensitive, m multiline, s dotall, u unicode — and see the result change instantly.

Built-in starting points

The "Common patterns" dropdown drops in ready-made expressions for emails, URLs, IPv4 addresses, dates, hex colors and phone numbers — a solid base to adapt rather than writing from a blank line. This uses the same JavaScript regex engine as your code, so a pattern that works here works in your String.match, replace and RegExp calls.

FAQ

Which regex flavor is this?

JavaScript (ECMAScript) regular expressions — the same engine Node and every browser use. Most syntax is shared across languages, but lookbehind, named groups and Unicode property escapes vary; test in the flavor you'll deploy in.

Why does my pattern match nothing / everything?

The usual culprits: forgetting to escape special characters like ., ( or +; a greedy .* swallowing more than intended (try the lazy .*?); or a missing g flag when you expect multiple matches. The live highlight makes these obvious.

Is my text sent anywhere?

No — the pattern runs against your text entirely in your browser. Nothing is uploaded, so you can test against sensitive logs safely.