When to Use This Regex Tester

Our free regex tester helps developers and data analysts with pattern matching tasks:

Form Input Validation
Test and debug patterns for email addresses, phone numbers, URLs, and other data formats before implementing them in your code.
Data Extraction & Parsing
Build and test regex patterns for extracting specific data from logs, documents, or web pages using capture groups.
Text Transformation
Create find and replace patterns to clean up text, reformat data, or transform strings in bulk operations.
Learning Regular Expressions
Use the pattern library and explanation feature to understand regex syntax and improve your regular expression skills.
Code Editor Integration
Test patterns for syntax highlighting, code linting, and search functionality in text editors and IDEs.

Frequently Asked Questions

What is a regular expression?: A regular expression (regex) is a sequence of characters that defines a search pattern. It's used for string matching, validation, search and replace, and text processing in programming.
Does this work with all regex flavors?: This tester uses JavaScript's native RegExp engine. Results may differ slightly in other languages like PHP (PCRE), Python, or Java due to syntax variations and feature support.
What do the regex flags do?: Use the 'g' flag for global matching, 'i' for case-insensitive, 'm' for multiline mode, 's' to make dot match newlines, and 'u' for full Unicode support.
How do I use capture groups in replace?: In the replace field, use $1, $2, etc. to reference captured groups. For example, matching (\w+)@(\w+) and replacing with $2:$1 swaps the parts.
Can I save my patterns?: Yes! Your patterns and test strings are automatically saved to your browser's local storage. You can also save named patterns and share them via URL.