Regex Tester
Test a regular expression against sample text with live match highlighting.
Text & data Client-side Native RegExp
Tool preview
How to use it
- 01
Enter the pattern and flags.
- 02
Paste the test text.
- 03
Inspect the matches or apply a replacement.
Limitations
- ! Catastrophic backtracking can freeze the tab on badly written patterns.
- ! Only JavaScript regular expression syntax is supported.
FAQ
Why do my matches disappear when I remove the g flag?
The tool adds g automatically so that all matches are listed.
Does it support lookbehind?
Yes in modern browsers, which support lookbehind natively.
Can I see capture groups?
The list shows full matches; group inspection is on the roadmap.
Files never leave your device
Processing happens in your browser using the File API, WebAssembly and Web Workers. There is no upload endpoint.
Technical details
- Processing
- Client-side
- Implementation
- Native RegExp
- Category
- Text & data
- Network requests
- None while processing