Regex Tester
Test and debug regular expressions with live matching.
Runs on your machine. Nothing you paste is uploaded.
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What it does
Write a JavaScript regular expression, paste some test text, and see every match listed with its position and capture groups. Toggle the g, i, m and s flags with one click, and the results refresh as you type. Syntax errors show up right under the pattern.
Matching runs in a background worker with a one-second limit, so a pattern with catastrophic backtracking stops with a timeout message instead of freezing the window. Ready-made samples for emails, URLs, IPs, dates, UUIDs, JWTs, hex colors and more give you a starting point to adapt.
When you would reach for it
- Build an email or URL validation pattern against a list of valid and invalid inputs.
- Check which capture groups a log-parsing pattern returns before putting it in code.
- Find out whether a pattern from a bug report backtracks badly on long input.
- See how the multiline and dotAll flags change what a pattern matches.
Also found by searching
- regex
- regular
- expression
- test
- match
- pattern