Regex Tester
Test and debug regular expressions with real-time matching, capture group highlighting, and a common regex pattern library.
Enter a regex pattern and test string to see results.
Frequently Asked Questions
What is a regular expression (regex)?
A regular expression is a sequence of characters that defines a search pattern. It is used for pattern matching within strings, commonly for validation, searching, and text manipulation in programming.
What are regex flags?
Regex flags modify how the pattern is applied. Common flags include: g (global - find all matches), i (case-insensitive), m (multiline - ^ and $ match line boundaries), s (dotAll - . matches newlines), and u (unicode - enables full Unicode matching).
What are capture groups in regex?
Capture groups are portions of a regex pattern enclosed in parentheses (). They allow you to extract specific parts of a match. For example, in the pattern (\d{3})-(\d{4}), each set of parentheses creates a capture group that extracts the digits separately.
How do I match an email address with regex?
A common email regex pattern is [a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}. This matches most standard email formats. You can find this and other common patterns in our built-in pattern library.
Is this regex tester free to use?
Yes, this regex tester is completely free with no signup required. Test as many patterns as you need with real-time matching and capture group analysis.