Regex Tester
Test regular expressions in real-time with match highlighting.
How to Use
Enter your regular expression in the pattern field, provide test strings in the input area, and see matches highlighted in real time. You can toggle flags like global (g), case-insensitive (i), and multiline (m). Capture groups are displayed separately so you can verify group extraction.
Common Use Cases
- Building and testing email or URL validation patterns before adding them to code
- Debugging regex-based log parsing rules for tools like Logstash or Fluentd
- Learning regular expressions interactively by experimenting with patterns
- Extracting structured data from unstructured text using capture groups
Frequently Asked Questions
Which regex engine does this tool use?
It uses the JavaScript RegExp engine built into your browser. Syntax is compatible with most modern regex flavors, though some advanced features like lookbehind may vary by browser.
Can I test regex replacements?
The tool focuses on matching and group extraction. For replacements, you can use the match results to verify your pattern is correct, then apply it in your code.
How do I match across multiple lines?
Enable the multiline (m) flag so that ^ and $ match the start and end of each line. Use the dotAll (s) flag if you want the dot (.) to also match newline characters.