🔍Regex Tester
Test and debug regular expressions.
🆓 Free🔒 Secure⚡ Instant📱 Mobile-friendly🚫 No signup
Test and debug regular expressions online for free. Syntax highlighting and real-time match results.
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g=global · i=ignore case · m=multiline · s=dotAll
How to Use Regex Tester — Step by Step
- 1Enter your regular expression in the pattern field (without surrounding slashes)
- 2Set flags — global (g), case-insensitive (i), multiline (m), as needed
- 3Paste the test string in the text area below — all matches are highlighted in real time
- 4Hover over any match to see its captured groups
Why Use ToolNest for Regex Tester?
- 🔍Live match highlighting updates as you type — no button needed
- 📋Shows all match groups and their captured values
- 🚩Toggle flags (g, i, m, s) with one click
- ⚡Runs entirely in the browser — your text never leaves your device
- 🆓Free — no sign up, no limits
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Frequently Asked Questions
Which regex flavor does the tester use?
The tester uses JavaScript's built-in RegExp engine. Syntax is mostly compatible with other languages but some features like lookbehind support vary by browser.
Does my test string get sent to a server?
No. All regex matching happens in your browser. Your text and pattern are never uploaded.
Can I test regex with flags?
Yes. Toggle global (g), case-insensitive (i), multiline (m), and dotAll (s) flags individually.
Is there a text length limit?
No enforced limit. The tester handles large text documents, though very long strings with complex patterns may be slow.