Regex Tester
Regular Expression Tester and Debugger
Test regular expressions with real-time matching. View capture groups, flags, and match details.
Highlighted
Matches
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How to use this tool
- Enter regex pattern (without delimiters)
- Select flags: global (g), case-insensitive (i), multiline (m), etc.
- Enter test string to match against
- View highlighted matches in real-time
- See capture groups and their values
- Check match indices and details
- Adjust pattern and see immediate results
About Regex Tester
The regex tester provides a live testing environment for regular expressions. Enter patterns and test strings to see matches highlighted instantly, view capture groups, check match positions, and validate regex syntax before using in code.
Supports JavaScript regex features including character classes, quantifiers, anchors, groups, lookaheads, lookbehinds, and flags. Real-time feedback helps debug complex patterns and understand regex behavior.
All testing happens locally. No patterns or test data are uploaded—safe for testing regex on sensitive data, confidential logs, or proprietary string formats.
Frequently asked questions
JavaScript regex flavor (ECMAScript standard). This differs slightly from other flavors like PCRE, Python, or .NET. For other languages, test with their specific regex engines when possible.
Enable the multiline (m) flag. This makes ^ and $ match line starts/ends, not just string start/end. Also test with realistic multi-line test strings to verify behavior.
Yes, but complex patterns on very large text may slow down browser. Regex complexity (backtracking, nested quantifiers) matters more than text size. Test on representative samples first.