Regex Tester
Real-time Regular Expression testing, match highlighting, and capture group analysis completely client-side.
About JavaScript Regular Expressions
SuperUtility offers an offline-first Regular Expression (Regex) Tester designed for developers, systems administrators, and data analysts. Regular expressions are powerful character pattern sequences used to perform advanced search, validation, parsing, and replacing operations in text documents.
This tester compiles standard JavaScript RegExp rules directly inside your browser engine. As you modify the search pattern or toggle flags like Global (`g`), Case-Insensitive (`i`), or Multiline (`m`), the tool highlights matching substrings instantly, compiles execution indexes, and itemizes captured groups to help you build complex patterns without guessing.
Frequently Asked Questions
What does the Global (g) flag do?
By default, a regular expression stops searching after finding the first matching substring. Toggling the Global (g) flag instructs the engine to scan the entire string, returning all matches.
How are Capture Groups analyzed?
Any pattern wrapped in parentheses `( )` creates a capture group. When matches are found, the tester isolates the content inside each group, allowing you to debug sub-string parameters easily.
Is my test data completely safe here?
Yes, 100%. Regular expression compiling and test text analysis occur strictly within your browser's memory sandbox. There are no server-side APIs involved, preventing leaks of confidential log logs.
Why does the interface freeze on some patterns?
Certain patterns with nested quantifiers can trigger Catastrophic Backtracking (a state of infinite complexity). We've built in a standard search guard threshold to automatically interrupt evaluation loops if matches exceed safe limits.
Common Regex Patterns & Cheatsheets
Useful Pattern Formats
Copy and paste these snippets to get started:
• Email: [a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}
• Phone: \+?\d{1,4}[-\s]?\(?\d{1,3}\)?[-\s]?\d{3}[-\s]?\d{4}
• URL: https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*)
• Hex: #[a-fA-F0-9]{6}Basic Token Reference
Standard operators for regular expressions:
• \d = any numeric digit [0-9] • \w = any word character [a-zA-Z0-9_] • \s = any whitespace, space, tab, line • . = any single character except newlines • * = zero or more repetitions • + = one or more repetitions • ? = optional character