Regex Tester

Frequently asked questions

Does this find only the first match, or every match?

Every match. The g flag is applied internally even if you don't type it, since without it a JavaScript regex only ever finds the first occurrence. Matching is capped at 1000 results, which only matters for pathological patterns against very large input.

Why does a pattern like /x*/ not freeze the page?

Patterns that can match a zero-length string (like x* or a lookahead-only pattern) would loop forever at the same position under naive global matching. This tool detects a zero-width match and advances one character before continuing, so it terminates instead of hanging.

Can I see named capture groups, not just numbered ones?

Yes. Named groups — (?<year>\d{4}) — appear alongside numbered groups, each with its own matched value and start/end position in the input.

Is my input uploaded anywhere?

No. Matching happens locally in your browser tab — nothing is sent to a server.