Regex Tester
Test regular expressions live with highlighted matches and group capture viewer.
About the Regex Tester
This regex tester highlights every match in your sample text as you type the pattern, and lists the capture groups for each one. Seeing matches appear and disappear while you edit is what makes a pattern quick to get right.
A regex tester replaces the alternative, which is editing a pattern in code and re-running until it works. Highlighting matches live means you see the effect of every character you add, and the moment a change breaks something.
Capture groups are the other half. A pattern that matches is only useful if the right parts are captured, and listing group contents per match shows immediately whether a group grabbed what you intended or swallowed too much.
Greediness causes most surprises. By default a quantifier takes as much as it can, so `.*` between two markers runs to the last one rather than the first. Adding a question mark makes it lazy — visible instantly here as the highlight shrinks.
How to use the Regex Tester
- Enter your pattern. Type the regular expression, with flags as needed.
- Paste sample text. Provide text that includes both cases that should match and cases that should not.
- Watch the highlights. Matches highlight live as you edit the pattern.
- Check the groups. Confirm each capture group holds what you expected.
Regex Tester features
- Real-time regex testing
- Pattern matching visualization
- Multiple regex flags
- Common regex templates
- Error detection
- Match highlighting
- Capture groups display
- Professional patterns
- Developer focused
- Advanced regex support
Frequently asked questions
How does regex testing work?
Our tester compiles regular expressions with JavaScript RegExp engine, applies patterns to test text, highlights matches in real-time, and provides detailed match information including groups, positions, and capture data.
What regex flags are supported?
Comprehensive flag support: g (global for all matches), i (case insensitive), m (multiline for line anchors), s (dot-all for newline matching), and combinations for flexible pattern matching behavior.
What common regex patterns are included?
Essential templates: email validation, URL matching, IPv4 addresses, date formats (YYYY-MM-DD), hex color codes, US phone numbers, numbers only, words only, and other frequently used patterns for quick implementation.
Can I test complex regex patterns?
Yes! Supports complex patterns including: lookaheads/lookbehinds, capture groups, quantifiers, character classes, anchors, boundaries, and advanced regex features for comprehensive pattern testing and debugging.
How are regex errors handled and displayed?
Real-time error detection identifies invalid syntax, quantifier issues, escape sequence problems, and pattern errors. Provides specific error messages and suggestions for regex debugging and correction.
What are the applications of regex testing?
Essential for: form validation, data extraction, text processing, log analysis, input sanitization, search functionality, data parsing, and pattern-based string manipulation across development projects.
Is this suitable for professional development?
Absolutely! Essential for web developers, backend engineers, data scientists, and software engineers. Perfect for API validation, data processing, text analysis, and professional regex development workflows.