Regex Tester
Test and debug regular expressions in real-time. See matches highlighted, capture groups extracted, and use common patterns — all in your browser.
About This Tool
- Real-time regex matching as you type
- Visual highlighting of all matches in the test string
- Capture group extraction and display
- Completely free with no registration required
Frequently Asked Questions
A regular expression (regex) is a sequence of characters that defines a search pattern. It's used for string matching, validation, and text manipulation in programming languages.
Flags modify how the regex behaves: 'g' (global) finds all matches, 'i' makes it case-insensitive, 'm' enables multiline mode, and 's' makes the dot match newline characters.
Capture groups are portions of the regex enclosed in parentheses (). They allow you to extract specific parts of a match. For example, (\d{4})-(\d{2}) captures year and month separately from a date.
Yes, poorly written regex with excessive backtracking can be slow. Avoid nested quantifiers like (a+)+ and use specific patterns. This tool helps you test performance in real-time.
Yes, completely free with no registration. Test as many regex patterns as you need.