How to use the Regex Tester
- Enter your pattern (without slashes) and choose flags
- Paste test text
- Review highlighted matches and the capture-group table
About this tool
The tester uses your browser’s own JavaScript regex engine, so behavior matches Node.js and front-end code exactly, including lookbehind, named groups (?<name>…) and Unicode property escapes like \p{L} (with the u flag). Matching is capped at 1,000 results to keep the page responsive.
| Pattern | Matches |
|---|---|
\d+ | One or more digits |
\b\w+@\w+\.\w+\b | Simple email address |
^\s*$ (m) | Blank lines |
(?<y>\d{4})-(?<m>\d{2}) | Year-month with named groups |
https?:\/\/\S+ | URLs |
Frequently asked questions
Which regex flavor is this?
JavaScript (ECMAScript). Most syntax is shared with PCRE, Python and Java, but some features, such as possessive quantifiers and recursion, are not supported.
What do the flags mean?
g finds all matches, i ignores case, m makes ^ and $ match at line breaks, s lets . match newlines, u enables full Unicode, and y anchors each match at lastIndex.
Why does my pattern freeze some testers?
Nested quantifiers like (a+)+ can trigger catastrophic backtracking. Matching runs only as you type and is capped, but simplify patterns like that for production code.
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