Free Regex Tester & Debugger

Our free regex tester is an essential tool for developers, data analysts, and anyone working with text pattern matching. Regular expressions (regex) are powerful sequences of characters that define search patterns, used in programming, text editors, and command-line tools for string matching, validation, and text manipulation.

What is Regular Expression (Regex)?

A regular expression is a sequence of characters that specifies a match pattern in text. Originally developed in theoretical computer science, regex has become an indispensable tool in modern programming. From validating email addresses to parsing log files, regex provides a concise and flexible way to identify strings of text such as particular characters, words, or patterns.

Key Features of Our Regex Tester:

• Real-time Testing: See matches instantly as you type your pattern
• Visual Highlighting: Matched text is highlighted in the test string
• Match Details: View index positions and captured groups for each match
• Flag Support: Toggle global (g), case-insensitive (i), multiline (m), and dotall (s) flags
• Pattern Validation: Instant feedback on regex syntax errors
• Example Patterns: Pre-built patterns for common use cases like emails, URLs, and dates
• Copy Functionality: One-click copying of patterns and test strings

Common Regex Use Cases:

• Email address validation and extraction
• URL parsing and validation
• Phone number formatting and validation
• Password strength requirements
• Log file parsing and analysis
• Data extraction from unstructured text
• Search and replace operations
• Input sanitization and validation

Understanding Regex Flags:

• g (Global): Find all matches rather than stopping after the first match
• i (Case Insensitive): Match both uppercase and lowercase letters
• m (Multiline): ^ and $ match start/end of each line, not just the string
• s (Dotall): Allows the dot (.) to match newline characters

Privacy & Security:

All regex testing happens entirely in your browser - no data is sent to external servers. Your patterns and test strings remain completely private. This makes our tool safe for testing patterns against sensitive data like API keys, passwords, or confidential information.

Tips for Writing Better Regex:

• Start simple and build complexity gradually
• Use character classes [abc] instead of alternation (a|b|c) when possible
• Be specific with quantifiers - use {n,m} instead of * or + when you know the range
• Use non-capturing groups (?:...) when you dont need to extract the group
• Test with edge cases including empty strings and special characters
• Consider using named capture groups for complex patterns

Whether youre a beginner learning regex or an experienced developer debugging complex patterns, our regex tester provides the instant feedback and detailed match information you need. Start testing your regular expressions now - simply enter your pattern above and see results in real-time.