Free Regex Tester
Test regular expressions with real-time matching, capture groups and common presets. 100% in your browser.
How It Works
Enter a regular expression pattern and test string. The tool highlights all matches in real-time as you type, showing match groups, capture groups, and their positions. Toggle flags (global, case-insensitive, multiline, dotAll) with checkboxes. See a detailed match breakdown with group indices. All processing runs locally in JavaScript.
When to Use It
- Building and debugging complex regex patterns for form validation, data extraction, or log parsing.
- Learning regular expressions interactively by seeing matches update as you modify the pattern.
- Testing regex patterns against sample data before deploying them in production code or CI pipelines.
Frequently Asked Questions
Which regex flavor does this use?
It uses JavaScript's native RegExp engine, which supports ECMAScript regex syntax including lookaheads, lookbehinds (ES2018+), named groups, and Unicode property escapes. Patterns written here will work directly in JavaScript, TypeScript, and Node.js code.
Can I test multiline patterns?
Yes. Enable the multiline (m) flag to make ^ and $ match the start and end of each line instead of the entire string. Enable dotAll (s) to make . match newline characters. Both are essential for parsing structured multiline text like logs or configuration files.
Is my test data sent to a server?
No. All regex matching runs entirely in your browser using JavaScript's RegExp engine. Your test strings — which may contain sensitive data like API keys, passwords, or personal information — never leave your device.
All calculations happen in your browser. No data is sent to any server.