Enter pattern and test string
Learn More About Regular Expressions
Master regex syntax and common patterns:
Online Regex Tester & Debugger
Test, debug, and learn Regular Expressions (Regex) online. A powerful regex tester with real-time highlighting, match information, and cheat sheets. Supports JavaScript regex flavor.
How It Works
Enter your regular expression and the test string. Our tool uses the browser's native JavaScript regex engine to evaluate the expression in real-time, highlighting all matches, capture groups, and providing detailed match information.
Common Use Cases
- Building and testing complex regex patterns for form validation (e.g., emails, passwords)
- Extracting specific data (like phone numbers or URLs) from large blocks of text
- Debugging regex patterns that are not matching the expected strings
- Learning how different regex tokens, quantifiers, and flags work interactively
Frequently Asked Questions
Our tool currently supports the JavaScript (ECMAScript) regular expression flavor, as it runs directly in your web browser.
Flags are optional parameters that modify the behavior of the regex. Common flags include 'g' (global, find all matches), 'i' (case-insensitive), and 'm' (multiline).
Yes. All regex evaluation happens locally in your browser. Your test strings and regex patterns are never sent to our servers.
The tool tests against JavaScript's RegExp engine. Most standard regex features like groups, lookaheads, character classes, and quantifiers are supported.
A common pattern is /^[\w.-]+@[\w.-]+\.[a-zA-Z]{2,}$/. However, email validation with regex is complex — for production, consider using a dedicated validation library.
g (global) finds all matches, not just the first. i (case-insensitive) ignores case. m (multiline) makes ^ and $ match start/end of each line instead of the whole string.
Wrap parts of your pattern in parentheses, e.g., /(\d{4})-(\d{2})-(\d{2})/. The tool highlights each group and shows the captured values separately.