Free Online Regex Tester & Debugger – Test Regular Expressions
Regular expressions (RegEx) are powerful patterns used for pattern matching, data validation, string parsing, and text searching across programming languages. However, writing and debugging complex regular expressions can quickly become frustrating without immediate visual feedback. Our free online Regex Tester and Debugger provides an interactive, real-time environment to test your regex patterns against any sample text. Easily toggle flags like global matching, case insensitivity, and multiline mode while instantly inspecting matched groups, indexes, and substitution replacements. Built with 100% client-side execution, your private text and data never leave your browser.
Key Features of Our Online Regex Tester & Debugger
Real-Time Matching
Instantly view matches, capture groups, and indices as you type your regex pattern or test string.
Flag Toggles
Quickly toggle standard flags including Global (g), Case-Insensitive (i), and Multiline (m).
Substitution & Replacement
Test string replacement patterns live to see how substitutions transform your input data.
How to Use the Regex Tester & Debugger
- Enter your regular expression pattern in the regex input field.
- Select your desired regex flags (g, i, m, s).
- Paste or type your test string into the subject text box to view live matches and details.
Frequently Asked Questions (FAQs)
Is my test data private?
Yes, all regex matching runs locally in your browser memory.
Which regex flavor is supported?
The tool uses standard JavaScript ECMAScript regular expression engine.