Which regular expression engine is used?
It uses your browser's native ECMAScript RegExp engine, ensuring full compatibility with modern JavaScript and TypeScript regex syntax.
Text
Test expressions with live match details.
Add an input and run this tool to see the output.
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Regex Tester Developer Guide
100% Client-Side & PrivateCheck a regular expression against sample text while reviewing matches and groups. Use the tester for development and debugging, not as a formal ReDoS proof.
Key capabilities
- Real-time regular expression matching against test strings
- Interactive match highlighting, captured group extraction, and index breakdown
- Full support for standard JavaScript regex flags (g, i, m, s, u)
- Built-in catastrophic backtracking guard to prevent browser tab freezes
Common use cases
- Testing email, phone number, and password validation patterns before writing frontend code
- Building and fine-tuning extraction rules for log parsing and text cleanup scripts
- Verifying regex replace rules and capture groups before running batch migrations
How to use Regex Tester
- Enter your regular expression pattern in the pattern input along with desired flags
- Type or paste sample text into the test string pane
- Examine highlighted matches, total match counts, and capture group indices in real time
Frequently asked questions
Can complex expressions crash my browser tab?
DevHub implements execution boundaries and input safeguards to minimize the risk of exponential catastrophic backtracking (ReDoS).