Test regular expressions with live match highlighting
Type a regular expression and some test text to see every match highlighted instantly, along with numbered and named capture groups and a live replacement preview.
Matches: 0
Contact: alice@example.com, bob@site.comRegex Tester: 3 simple steps
- 1
Enter your pattern and choose flags.
- 2
Paste the text you want to test.
- 3
Read the highlighted matches, groups and the replacement result.
It uses your browser's JavaScript regex engine, so what you see here is what runs in Node.js and front-end code. Flags such as global, case-insensitive, multiline and dotAll can be toggled with a click.
Built for speed and privacy
- Live highlighting as you type
- Numbered and named capture groups
- Replacement preview with $1 and $<name>
- Safe: runs locally with a match limit
Regex Tester FAQ
JavaScript (ECMAScript). Lookbehinds, named groups and Unicode property escapes are supported in modern browsers.
g finds all matches, i ignores case, m makes ^ and $ match at line boundaries, s lets . match newlines, u enables Unicode mode and y matches only at the last index.
Check for unescaped special characters such as . ( ) + ? and make sure the right flags are enabled. Backslashes should be written once here, not doubled as in a string literal.
Catastrophic backtracking is possible with some patterns. The tester stops after a large number of matches, but if it stalls, simplify the pattern.
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