RegEx Tester
Test and debug JavaScript regex patterns with live match highlighting
Loading RegEx Tester...
⚙️ How It Works
Enter a regex pattern and select flags, then provide test text. Matches are highlighted in real time, with detailed breakdowns including index positions and capture groups.
❓ Frequently Asked Questions
Which RegEx engine does this tool use?
It uses your browser's native JavaScript RegExp engine, so results match real-world JS behavior.
Which flags are supported?
You can toggle common flags like global (g), case-insensitive (i), multiline (m), and dotAll (s).
Can I inspect capture groups?
Yes. Any groups defined with parentheses are listed with their matched values for each result.
Does it highlight all matches?
Yes. When matches are found, they are highlighted directly in the input text along with their positions.
Is my data sent anywhere?
No. All pattern matching runs locally in your browser.
Does it support advanced regex features?
Yes. Most modern JavaScript features like lookaheads and (in supported browsers) lookbehinds are supported.
Does the RegEx Tester work offline?
Yes, the RegEx Tester is fully functional offline. Because this tool runs entirely in your browser, no data is ever uploaded to external servers. Once the page is loaded, you can seamlessly continue using it without an active internet connection. You can also install Knicknaks as a Progressive Web App (PWA) for native-like offline access.