Regex Tester — Test Regular Expressions Online Free
DeveloperTest and debug regular expressions with live match highlighting, flag toggles and 8 common presets. Uses the JavaScript regex engine. Free online regex tester tool.
Quick Presets
About the Regex Tester — Test Regular Expressions Online Free
Our free regex tester provides a live, interactive environment for writing and testing regular expressions. Enter your pattern, toggle flags (global, case-insensitive, multiline, dotAll) and see all matches highlighted in real time. Matches are listed with their positions. Eight common presets — email, URL, phone, IPv4, hex color, date, numbers, words — are included as starting points. Uses JavaScript's native RegExp engine.
How to Use the Regex Tester — Test Regular Expressions Online Free
- 1
Enter your regex pattern in the pattern field (without surrounding / / slashes).
- 2
Set flags using toggle buttons — g, i, m, s.
- 3
Or click a preset like email or URL.
- 4
Type your test string and see matches highlighted in real time.
Frequently Asked Questions
What regex engine does this use?
JavaScript's ECMAScript regex engine — the same as Node.js and browser JavaScript. Supports character classes, quantifiers, groups, lookaheads and named capture groups.
How do I match an email?
Pattern: [a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,}. Click the Email preset to load this automatically.
What are regex flags?
g: find all matches. i: case-insensitive. m: ^ and $ match start/end of each line. s: dot matches newlines.
Can I test multiple cases at once?
Yes. Add multiple test strings in your test box — valid, invalid and edge cases — and see live highlighting for each.