Regex Tester
Type a pattern and some text to test it against — matches, capture groups, and a live replacement preview all update as you type. Matching runs using your browser's own JavaScript engine, so nothing you enter ever leaves this page.
Batch mode
Why test regex in the browser?
Regex testers are a classic "paste something you're actively working on" tool — often a log
line, a URL pattern, or a validation rule pulled straight out of production code. Nothing you
paste here is ever sent to a server —
see why that matters.
Matching, capture groups, and the replacement preview are all recomputed on every keystroke
using your browser's own RegExp engine — check
your network tab while you use it.
Flags reference
This tool matches using JavaScript's native RegExp
(the ECMAScript flavor) — mostly compatible with PCRE (Python, PHP, grep -P), but not identical,
so a pattern copied from another language's docs can behave slightly differently here.
- g
- Global — find all matches instead of stopping at the first.
- i
- Case-insensitive matching.
- m
-
^and$match the start/end of each line, not just the whole string. - s
- Dot-all — lets
.also match newline characters. - u
- Unicode mode — treats the pattern and string as full Unicode code points, not UTF-16 code units.
- y
- Sticky — matches only starting at the current position, rather than scanning forward.
FAQ
Why does my pattern match zero results even though it looks right?
The usual culprits: a special character (. * + ? ( ) [ ] ^ $ |) that needed escaping but wasn't, a greedy quantifier consuming more than intended, or
forgetting the i flag when the text's case doesn't
match the pattern.
Are named capture groups supported?
Yes — (?<name>...) groups are supported
by JavaScript's engine and shown separately from numbered groups in the match results above.
Related tools
- JSON Formatter & Validator — Format, validate and minify JSON; points to the exact error line.
- Format Identifier — Paste anything to find out what it is (a JWT, JSON, a certificate, Base64, a cron schedule and more), then open it in the right tool.