Regex Tester
Test regular expressions online with real-time match highlighting. Supports all JavaScript regex flags (g, i, m, s, u). Capture groups, named groups, and replace mode.
Write and test regex patterns against your input with live match highlighting as you type. All JavaScript flags are supported: global (g), case-insensitive (i), multiline (m), dotAll (s), and Unicode (u). Capture groups and named capture groups are shown individually. Use replace mode to preview substitutions before applying them in code. Useful for validating emails, parsing log files, and building input validation patterns.
Frequently Asked Questions
- Which regex engine does the tester use?
- The tester uses the JavaScript RegExp engine built into your browser, so results match exactly what you would see in JavaScript code.
- Are lookaheads and lookbehinds supported?
- Yes, modern regex features including lookaheads, lookbehinds, and named capture groups are supported in all modern browsers.
- Is this tool free to use?
- Yes, all tools on Here Be Tools are completely free with no signup or account required.
- Is my data sent to a server?
- No. All processing happens locally in your browser. No data you enter is ever transmitted to any server.