Regex Tester
Our advanced regex tester is the ultimate online tool for developers, data analysts, and system administrators who need to build, test, and debug regular expressions with precision. This comprehensive regex validator supports JavaScript, Python, PHP, and PCRE regex flavors, providing real-time pattern matching, syntax highlighting, and detailed match analysis. Perfect for validating email patterns, parsing log files, extracting data from text, testing regex replacements, and debugging complex pattern matching logic across multiple programming languages and development environments.
Matches email addresses
\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\bURL
Matches HTTP/HTTPS URLs
https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*)Phone (US)
Matches US phone numbers
$$?([0-9]{3})$$?[-. ]?([0-9]{3})[-. ]?([0-9]{4})IP Address
Matches IPv4 addresses
\b(?:[0-9]{1,3}\.){3}[0-9]{1,3}\bDate (MM/DD/YYYY)
Matches MM/DD/YYYY format
\b(0?[1-9]|1[0-2])\/(0?[1-9]|[12][0-9]|3[01])\/(19|20)\d\d\bHex Color
Matches hex color codes
#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})Credit Card
Matches credit card numbers
\b(?:\d{4}[-\s]?){3}\d{4}\bUsername
Matches usernames (3-16 chars, alphanumeric + underscore)
^[a-zA-Z0-9_]{3,16}$Password
Strong password (8+ chars, mixed case, number, special char)
^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&])[A-Za-z\d@$!%*?&]{8,}$HTML Tag
Matches HTML tags
<\/?[a-z][a-z0-9]*[^<>]*>Enter Regex Pattern
Type your regular expression pattern and set flags
Add Test String
Enter the text you want to test against your regex
View Results
See highlighted matches and capture groups instantly
Advanced Regular Expression Tester and Debugger
Our comprehensive regex tester provides a powerful environment for developing, testing, and debugging regular expressions across multiple programming languages and platforms. This essential developer tool supports JavaScript, Python, PHP, and PCRE regex flavors, enabling you to create and validate pattern matching logic with confidence. Whether you're parsing log files, validating user input, or extracting data from text, this tool ensures your regular expressions work correctly before implementation.
Real-time pattern matching provides instant feedback as you develop regular expressions, highlighting matches, groups, and captures in your test text. The interactive interface shows exactly which parts of your text match the pattern, making it easy to understand how your regex behaves with different inputs. Advanced highlighting distinguishes between full matches, capturing groups, and named groups, providing clear visual feedback that accelerates regex development and debugging.
Multi-language support ensures your regular expressions work correctly across different programming environments. Test JavaScript regex for web applications, Python patterns for data processing scripts, PHP expressions for server-side validation, and PCRE patterns for system administration tasks. Each flavor includes language-specific features and syntax variations, helping you write portable regex patterns or optimize them for specific platforms and use cases.
Comprehensive testing features include match extraction, replacement testing, and performance analysis. View all matches in your test text, test replacement patterns with substitution previews, and analyze regex performance to identify potentially problematic patterns. The tool provides detailed information about capturing groups, named captures, and match positions, essential for complex text processing tasks and data extraction workflows.
Educational resources integrated into the tester help developers learn regular expression syntax and best practices. Interactive examples demonstrate common patterns for email validation, phone number formatting, URL parsing, and data extraction. Syntax reference guides explain metacharacters, quantifiers, and advanced features, while performance tips help you write efficient patterns that scale well with large datasets and high-volume applications.
The responsive design ensures optimal functionality across desktop development environments and mobile devices, allowing you to test and debug regular expressions wherever you work. Privacy-focused architecture processes all regex testing locally in your browser, ensuring that sensitive data and proprietary patterns never leave your device. Export functionality allows you to save tested patterns and generate code snippets for immediate integration into your projects, streamlining the development workflow from testing to implementation.
Frequently Asked Questions - Regex Tester
How does this free regex tester help debug regular expressions?
Our advanced regex tester provides real-time pattern matching with instant visual feedback, highlighting matches, capture groups, and named groups in your test text. The tool supports JavaScript, Python, PHP, and PCRE regex flavors, making it perfect for cross-platform development. You can test complex patterns, validate email addresses, parse log files, and debug regex syntax errors with detailed explanations and match analysis.
What regex flavors and programming languages are supported?
Our regex tester supports multiple regex flavors including JavaScript (ECMAScript), Python (re module), PHP (PCRE), and standard PCRE patterns. Each flavor includes language-specific features and syntax variations, helping you write portable regex patterns or optimize them for specific platforms. The tool automatically adjusts syntax highlighting and validation based on your selected regex flavor.
How do I test regex patterns with flags and modifiers?
Enable regex flags like global (g), case-insensitive (i), multiline (m), and dotall (s) using our intuitive flag selector. The tool shows how flags affect pattern matching behavior and provides examples of common flag combinations. You can test complex patterns with multiple flags to ensure they work correctly in your target programming environment.
Can I test regex replacement patterns and substitutions?
Yes! Our regex tester includes replacement testing functionality where you can test substitution patterns with backreferences, named groups, and replacement functions. Preview how your regex replacements will transform text before implementing them in your code. This feature is essential for data cleaning, text processing, and content transformation workflows.
How does the regex match highlighting and visualization work?
Our visual regex matcher highlights all pattern matches in your test text with different colors for full matches, capturing groups, and named groups. The tool shows match positions, group numbers, and captured content in an organized display. This visual feedback makes it easy to understand complex regex behavior and debug pattern matching issues quickly.
What are some common regex patterns I can test with this tool?
Test popular patterns like email validation (/^[^\s@]+@[^\s@]+\.[^\s@]+$/), phone number formatting, URL parsing, IP address validation, date extraction, and log file parsing. Our tool includes a pattern library with pre-built regex examples for common use cases. You can modify these patterns and test them against your specific data requirements.
How do I debug regex performance and avoid catastrophic backtracking?
Our regex tester provides performance analysis to identify potentially slow patterns that could cause catastrophic backtracking. The tool highlights problematic constructs like nested quantifiers and suggests optimizations. Test your patterns against large text samples to ensure they perform well in production environments and won't cause application timeouts.
Is my regex pattern and test data secure when using this tool?
Absolutely! All regex testing occurs entirely in your browser using client-side JavaScript. No patterns, test data, or results are transmitted to our servers or stored anywhere. This ensures complete privacy for sensitive data, proprietary patterns, and confidential text processing requirements. The tool works offline once loaded for maximum security.
Can I save and export my tested regex patterns?
Yes! Copy your tested regex patterns to the clipboard with proper escaping for your target programming language. The tool formats patterns correctly for JavaScript, Python, PHP, and other languages. You can also save pattern libraries locally and share working regex solutions with your development team while maintaining proper syntax formatting.
How do I test regex patterns with large text files and datasets?
Our regex tester handles large text inputs efficiently with optimized processing algorithms. Paste large log files, CSV data, or text documents to test your patterns against realistic datasets. The tool provides match statistics, processing time analysis, and memory usage information to help you optimize patterns for production use with large data volumes.
What regex learning resources are available in this tool?
Access built-in regex syntax references, common pattern examples, and interactive tutorials that explain metacharacters, quantifiers, and advanced features. The tool provides context-sensitive help, pattern explanations, and best practice recommendations. Learn regex concepts through hands-on testing with immediate visual feedback and practical examples.
How do I handle special characters and escaping in regex patterns?
Our regex tester automatically handles character escaping and provides guidance on special regex metacharacters like . * + ? ^ $ { } [ ] \ | ( ). The tool shows how to escape these characters when you need to match them literally and explains the difference between regex metacharacters and literal characters. Visual highlighting helps identify escaped vs unescaped characters in your patterns.