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.
Related Tools
IP Address Checker
Check your public IP address, location and device details.
Color Code Converter
Convert between HEX, RGB, and HSL color formats instantly.
CSS Minifier
Minify and beautify CSS code to reduce file size instantly.
JS Minifier
Minify JavaScript code to reduce file size and improve load times.