About this tool
The Regex Tester lets you build and debug regular expressions with live matching, group highlights, and clear error messages. Flags like case insensitivity, multiline, and global match are just a toggle away.
Regex Tester
Test regular expressions with real-time highlighting and match details.
//g
Common Patterns
How to use
- Write your regex pattern in the top input.
- Toggle flags such as g (global), i (case-insensitive), and m (multiline).
- Paste or type the test text below.
- See matches highlighted inline and listed by group.
- Copy the regex or the matched results when ready.
Common use cases
- Extracting email addresses from a block of text.
- Validating a form field like a phone number.
- Rewriting dates from one format to another with capture groups.
- Finding log entries that match a given level or component.
- Debugging a regex that is matching too much or too little.
Frequently asked questions
Which regex flavor is used?
JavaScript regex, because the tool runs in your browser. Most patterns port cleanly to other languages; look up edge cases like lookbehind when in doubt.
How do I match across multiple lines?
Enable the m flag so ^ and $ treat each line as a separate boundary, and the s flag so . matches newlines.
Why does my regex work in one tool but not another?
Different engines support different features. Features like named groups or atomic groups may not exist everywhere.
Is my test text uploaded?
No. Testing runs entirely in your browser.