About the regex tester
A regex tester lets you build and check regular expressions against your own text in real time. Enter a pattern and flags, paste a test string, and see every match highlighted with its capture groups. You can also test a replacement. It is the fastest way to write, debug and learn regular expressions, and it runs entirely in your browser.
How Regex Tester works
How to test a regular expression
- Type your pattern and choose flags (g, i, m, s and more).
- Paste the text you want to test against.
- Matches are highlighted live, with capture groups listed; try a replacement to see the result.
Flags explained
g finds all matches, i ignores case, m makes ^ and $ match each line, and s lets . match newlines. Combine them as needed.
Learn and debug faster
Seeing matches and groups update as you type makes it easy to fix a pattern that matches too much or too little — far quicker than testing in code.
Common uses
- Build and debug a regex pattern
- Validate input formats (email, phone, etc.)
- Extract data with capture groups
- Test find-and-replace rules
- Learn regular expressions interactively
- Check a pattern before using it in code
- Search text with complex rules
- Verify edge cases quickly
Frequently asked questions
How do I test a regex?
Enter your pattern and flags, paste your text, and matches are highlighted instantly with their groups.
What flags are supported?
Common JavaScript flags: g (global), i (ignore case), m (multiline), s (dotall) and others.
Can I test a replacement?
Yes — enter a replacement string to preview the result, including group references like .
Which regex flavour is this?
JavaScript (ECMAScript) regular expressions, as used in browsers and Node.js.
Is my text uploaded?
No — everything is tested in your browser.
Why does my pattern not match?
Check your flags, escaping of special characters, and that the pattern fits the text exactly.
Does it show capture groups?
Yes — each match lists its numbered capture groups.
Is it free?
Yes — completely free with no sign-up.