What is a Regex Tester?
A Regular Expression (Regex) is a sequence of characters that specifies a search pattern, commonly used by developers for string matching, search-and-replace tasks, and input validation. However, writing regex can be incredibly tricky. Our Free Regex Tester & Debugger allows you to write your regex pattern and instantly see the matches highlighted in your test string. It supports JavaScript-flavored regex and updates in real-time as you type.
Understanding Regex Flags
- Global (g): By default, regex stops after the first match. The 'g' flag tells the engine to continue searching for all possible matches throughout the entire string.
- Case Insensitive (i): Makes the expression ignore uppercase and lowercase differences. For example,
/test/iwill match "Test", "TEST", and "test". - Multiline (m): Changes the behavior of
^(start) and$(end) to match the start and end of individual lines within a multi-line string, rather than just the beginning and end of the whole string.
Is My Test Data Secure?
Yes. Developers often use real data, logs, or sensitive emails to test their regex patterns. This tool runs 100% locally in your browser using the native JavaScript regex engine. None of your patterns, expressions, or test strings are ever uploaded or saved to our servers. Your data stays entirely on your device.