About the Regex Tester
Build and debug regular expressions with instant feedback. Type a pattern and test text, and every match is highlighted live with its capture groups listed — ideal for validation patterns, search-and-replace and log parsing.
Frequently Asked Questions
How do I test a regex?
Type the pattern, add flags if needed, and paste your test text. Matches highlight instantly.
Which regex flavour is used?
JavaScript (ECMAScript) regular expressions, as used in browsers and Node.js.
What do the g, i and m flags do?
g finds all matches, i ignores case, m makes ^ and $ match at line breaks.
What is a capture group?
Part of a pattern in parentheses whose matched text is captured separately — e.g. (\d{4}) captures a year.
What is a regex for email validation?
A practical pattern is ^[^\s@]+@[^\s@]+\.[^\s@]+$ — full RFC validation is far more complex.
How do I match a phone number?
It depends on the format; for 10 digits: ^\d{10}$.
Why doesn’t my regex match?
Check escaping of special characters like . ? + ( ) and missing flags.
What does .* mean?
Any character (.) repeated zero or more times (*).
Does the Regex Tester send or save my data?
No, matching runs in your browser.
Is the Regex Tester free to use?
Yes.