Type a regex and see matches highlighted in real time against your test string. Includes capture groups, flag toggles, and plain-English explanation.
Regex Tester is a browser-based tool on 24Toolkit. Type a regex and see matches highlighted in real time against your test string. Includes capture groups, flag toggles, and plain-English explanation. The Online Regex Tester is a sophisticated developer utility designed to build, test, and debug Regular Expressions (RegEx) in real-time. Regular expressions are powerful sequences of characters that define search patterns, commonly used for string matching, data validation, and text transformation. While powerful, RegEx syntax can be notoriously difficult to get right without immediate feedback. Our tool solves this by providing instant visual highlighting of matches as you type. Built with performance and security in mind, this tester supports various JavaScript regex flags like global (g), case-insensitive (i), and multiline (m). It includes a built-in safety check to detect 'Evil Regex' patterns that might cause Regular Expression Denial of Service (ReDoS) attacks.
Key Features
Test regex patterns
Live matching
Global, case-insensitive flags
100% client-side
Free with no limits
How to Use
Enter your Regular Expression pattern in the top field (e.g., [a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,}).
Specify your search flags in the small input box; 'g' (global) is usually recommended to find all matches.
Paste the text you want to search through into the 'Test String' area.
Observe the real-time highlighting in the results card and click individual matches to copy them to your clipboard.
FAQ
What regex flavor is used?
JavaScript RegExp (ECMAScript). Flags: g (global), i (case-insensitive), m (multiline).
Does my test text leave the browser?
No. Regex matching uses the browser's native RegExp engine. Your patterns and test strings remain in browser memory and are never transmitted — safe for testing patterns against sensitive data.
Why does my pattern not match?
Check escaping (e.g., \d for digits), flags, and syntax. Use a regex reference for help.