Regex Tester
Tests regular expressions against sample text in real time, with configurable flags, highlighted matches, capture groups, and match index details.
Flags
Preview (2 matches)
Match details
#1 at index 14: support@example.com
#2 at index 37: sales@example.co
Regex Tester — Free Online Tool
Tests regular expressions against sample text in real time, with configurable flags, highlighted matches, capture groups, and match index details.
How to use the Regex Tester
- Open the tool above — it runs entirely in your browser, so your input never leaves this page.
- Paste or type your input into the field, then press the relevant button (e.g. Encode / Decode, Generate, or Convert).
- Copy the result from the output area with the copy button orCtrl/Cmd + C.
- No signup, no upload, and no tracking — repeat as often as you need.
Frequently asked questions
Which regex flavor does the tester use?
It uses the JavaScript-flavored regular expression engine built into your browser, so constructs like lookahead, capture groups, and flags behave exactly as they do in Node.js and modern browsers.
Does the regex tester show capture groups?
Yes. It highlights every match and lists each capture group's value and index for both matches and the overall matched ranges.
Free & private — why use this Regex Tester
The Regex Tester runs 100% client-side in your browser. Your data is never uploaded to a server, no account is required, and the tool is completely free. It works offline once the page has loaded and is part of a growing collection of privacy-first developer utilities.