How to Test a Regular Expression (Regex) Online
Regular expressions are powerful but easy to get subtly wrong. Testing a pattern against real sample text — and seeing exactly what matches — is the fastest way to get it right. Kitolity’s regex tester runs entirely in your browser.
The tool
Regex Tester
Step by step
- Open the Regex TesterGo to the Regex Tester in your browser.
- Enter your patternType your regular expression and any flags (e.g. g, i, m).
- Paste sample textAdd the text you want to match against.
- See the matchesWatch matches highlight live as you refine the pattern.
Common regex gotchas
Remember that ., *, +, ?, (), [], {}, ^, $, and \ are special — escape them with a backslash to match them literally. Use the i flag for case-insensitive matching and g to find all matches, not just the first. Anchors ^ and $ match start and end of a line (or string).
Why test against real text?
A pattern that looks right often over- or under-matches on real data. Testing against representative samples — including the edge cases you expect to fail — catches those problems before the regex ships in your code.
Frequently asked questions
Is my text uploaded?
No — matching runs entirely in your browser, so your pattern and text stay on your device.
Does it highlight matches?
Yes — matches update live as you edit the pattern.
Is it free?
Yes, completely free with no sign-up.