Regex Tester
Test a regular expression against any string with live match highlighting and capture groups. Starts with an example.
Reading the results
Every match is highlighted in the test string and listed below. If your pattern has
parentheses, each match also shows its capture groups — the sub-strings the
groups extracted. Add the g flag to find every match rather than just the first.
Frequently asked questions
What is a regular expression?
A regular expression (regex) is a pattern used to match text — finding, validating or extracting parts of a string. They power search-and-replace, form validation and data parsing.
How do I use this tester?
Type a pattern and flags, then a test string. Matches are highlighted live and listed below with any capture groups. It starts pre-loaded with a working example so you can see how it behaves.
What do the flags mean?
Common flags: g (global — find all matches), i (case-insensitive), m (multiline ^ and $), s (dot matches newlines). This tester uses JavaScript regex syntax.
What are capture groups?
Parentheses in a pattern create capture groups that extract sub-parts of a match. For example, (\w+)@(\w+) captures the user and domain separately.