Which regex flavor does this tool use?

The tool uses JavaScript regular expression syntax, which covers the vast majority of use cases. It supports flags like g (global), i (case-insensitive), m (multiline) and s (dotAll).

Can I see capture groups?

Yes. Each capture group is highlighted in a different color, and the matched group values are listed below the test string for every match found.

Is my test data private?

Yes. All regex evaluation happens in your browser using JavaScript. No data is sent to any server, making it safe to test patterns against sensitive log data or PII.

Test Regex Online Free

Write a regular expression and see matches highlighted in real time against your test string. This free tool helps you debug complex patterns, understand capture groups and validate regex syntax without leaving your browser.

Open Regex Tester

Example: Email Validation

Pattern: /^[\w.-]+@[\w.-]+\.[a-zA-Z]{2,}$/gm

Test String:
  [email protected]      ✅ Match
  [email protected]      ✅ Match
  [email protected]           ❌ No match
  @missing-local.com     ❌ No match

Common Use Cases

Building validation patterns for forms and user input
Extracting data from log files with capture groups
Testing search-and-replace patterns before applying them
Learning regex syntax with instant visual feedback

Frequently Asked Questions

Which regex flavor does this tool use?: The tool uses JavaScript regular expression syntax, which covers the vast majority of use cases. It supports flags like g (global), i (case-insensitive), m (multiline) and s (dotAll).
Can I see capture groups?: Yes. Each capture group is highlighted in a different color, and the matched group values are listed below the test string for every match found.
Is my test data private?: Yes. All regex evaluation happens in your browser using JavaScript. No data is sent to any server, making it safe to test patterns against sensitive log data or PII.