Regex Tester & Pattern Builder
Professional regular expression tester with live pattern matching, syntax highlighting, replace functionality, and comprehensive pattern library. Test, debug, and perfect your regex patterns instantly.
Regular Expression Pattern
Test String
Matches (0)
Enter a pattern and test string to see matches
Replace
Why Use Our Regex Tester?
Comprehensive regex toolkit with advanced features for developers, data analysts, and text processing experts
Live Pattern Matching
See regex matches highlighted in real-time as you type. Instant visual feedback for debugging patterns.
Comprehensive Flag Support
Full support for all regex flags: global, multiline, ignoreCase, sticky, unicode, and dotAll modes.
Groups & Named Groups
Detailed breakdown of capture groups and named groups with position tracking and value extraction.
Pattern Library
Extensive library of common regex patterns for emails, URLs, dates, phone numbers, and more.
Replace & Substitute
Test find-and-replace operations with group references and pattern substitutions.
Pattern Explanation
Interactive pattern explanation showing flag meanings and regex behavior details.
File Processing
Upload text files, logs, or data files to test patterns against large datasets.
Export Results
Download test results as JSON with match details, groups, and replacement outputs.
Real-time Validation
Instant regex syntax validation with detailed error messages for debugging.
Easy Sharing
Copy patterns, matches, or results to clipboard for sharing and documentation.
Privacy Focused
All processing happens locally in your browser - no data is transmitted to servers.
High Performance
Optimized for handling large text inputs and complex patterns with minimal latency.
Common Regex Use Cases
Practical applications where our regex tester excels
Email Validation
Validate email addresses in forms and user input
^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$Examples:
user@example.comtest.email+tag@domain.co.ukPhone Number Extraction
Extract phone numbers from text in various formats
\+?1?[-.(]?(\d{3})[-.)\s]?(\d{3})[-.]?(\d{4})Examples:
(555) 123-4567+1-555-123-4567555.123.4567URL Detection
Find and extract URLs from web content
https?:\/\/(?:[-\w.])+(?::[0-9]+)?(?:\/(?:[\w\/_.])*)?(?:\?(?:[\w&=%.])*)?(?:\#(?:[\w.])*)?Examples:
https://example.comhttp://site.org/page?param=valueDate Format Parsing
Parse dates in MM/DD/YYYY or DD/MM/YYYY format
\b(\d{1,2})[\/\-](\d{1,2})[\/\-](\d{4})\bExamples:
12/25/202301-01-20243/15/2023Password Strength
Validate strong passwords with complexity requirements
^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&])[A-Za-z\d@$!%*?&]{8,}$Examples:
MyPass123!Secure@2024Complex#Pass99IP Address Validation
Validate IPv4 addresses and network configurations
^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$Examples:
192.168.1.110.0.0.1255.255.255.255Regex Syntax Quick Reference
Essential regex patterns and syntax for effective pattern matching
Basic Patterns
.Any character*0 or more+1 or more?0 or 1^Start of line$End of lineCharacter Classes
\dAny digit\wWord character\sWhitespace[abc]Any of a, b, c[a-z]Any lowercase[^abc]Not a, b, or cGroups & Quantifiers
(abc)Capture group(?:abc)Non-capture{3}Exactly 3{3,}3 or more{3,5}Between 3 and 5a|ba or bFrequently Asked Questions
What is a regular expression (regex)?
A regular expression is a sequence of characters that defines a search pattern. It's used for pattern matching within strings, finding and extracting data, validation, and text processing. Regex is supported in most programming languages and text editors.
How do I test if my regex pattern is working?
Enter your regex pattern in the pattern field, add your test text, and see immediate results. Matches are highlighted in yellow, and detailed information about each match, including groups and positions, is displayed in the matches section.
What are regex flags and when should I use them?
Regex flags modify how the pattern matching works. Common flags include: global (g) for finding all matches, ignoreCase (i) for case-insensitive matching, multiline (m) for treating ^ and $ as line boundaries, and dotAll (s) for making . match newlines.
How do I use capture groups in regex?
Capture groups are created using parentheses () and allow you to extract specific parts of a match. For example, in the pattern (\d{3})-(\d{2})-(\d{4}) for SSN format, each group of parentheses captures the respective number groups, which you can reference in replacements as $1, $2, $3.
Can I upload files to test large amounts of text?
Yes! Use the "Upload File" button in the test string section to load text files, logs, CSV files, or JSON data. This is perfect for testing patterns against large datasets or real-world data files.
How do I use the replace functionality?
Enter your replacement text in the replace field. You can use $1, $2, etc. to reference capture groups from your pattern. For example, if your pattern captures first and last names, you could use "$2, $1" to swap their order.
Is my data safe when using this tool?
Absolutely! All regex testing happens entirely in your browser - no data is sent to our servers. Your patterns, test strings, and results remain completely private and secure on your device.
How can I save or share my regex patterns?
Use the copy buttons to copy patterns, matches, or results to your clipboard. You can also download a JSON file with all test results, patterns, and match details using the "Download Results" button for documentation or sharing.
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