Regex Tester
Test regular expressions in real time with match highlighting, capture group extraction, and support for all standard regex flags.
Get notified the day we launch. No spam, ever.
What to expect
Built for developers
Write and test regular expressions with real-time highlighting, capture group display, and support for global, case-insensitive, multiline, and dotAll flags.
Runs client-side. Your data never leaves your browser.
No ads, no trackers, no popups. Pure focus.
Paste code or upload files. Both modes supported.
Share output with teammates via a permanent link.
Adapts to your system preference automatically.
Fully responsive. Works on any screen size.
About this tool
OpenFormatter's Regex Tester lets you test regular expressions online for free. Supports JavaScript regex syntax with flags (g, i, m, s, u, y). Shows all matches highlighted in real time, displays capture groups and named groups, provides match count, and explains regex tokens. All processing happens in your browser — no data is sent to any server.