Free Regex Tester
Test and debug your regular expressions instantly with our powerful regex tester. Get real-time pattern matching, capture groups analysis, and detailed explanations to perfect your regex patterns.
Test Your Regex Pattern
Enter your regular expression pattern and test text to see matches in real-time
Match Results
Enter a regex pattern and test text to see results
Regex Tester Guide
Master regular expressions with our comprehensive guide and testing tool
How to Use the Regex Tester
Step 1: Enter Your Pattern
Type your regular expression in the pattern field. Don't include delimiters like forward slashes unless they're part of your pattern.
Step 2: Add Test Text
Enter the text you want to test your pattern against. You can paste multiple lines and large blocks of text.
Step 3: Set Flags
Choose flags like case insensitive, multiline, or dot all to modify how your pattern behaves.
Step 4: View Results
See real-time matches, capture groups, execution time, and pattern analysis in the results panel.
Regular Expression Basics
Character Classes
. Matches any character except newline\d Matches any digit (0-9)\w Matches word characters (a-z, A-Z, 0-9, _)\s Matches whitespace characters[a-z] Matches any lowercase letter[0-9] Matches any digitQuantifiers
* Zero or more occurrences+ One or more occurrences? Zero or one occurrence{"n"} Exactly n occurrences{"n,m"} Between n and m occurrences{"n,"} n or more occurrencesAnchors and Boundaries
^ Start of string/line$ End of string/line\b Word boundary\B Non-word boundaryCommon Regex Patterns
Email Address
[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]2Matches standard email addresses like user@example.com
US Phone Number
\(\d3\)\s\d3-\d4Matches phone numbers in format (555) 123-4567
URL
https?://[^\s]+Matches HTTP and HTTPS URLs
IPv4 Address
((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]?)Matches valid IPv4 addresses like 192.168.1.1
Date (ISO Format)
\d4-\d2-\d2Matches dates in YYYY-MM-DD format
Hex Color Code
#([A-Fa-f0-9]6|[A-Fa-f0-9]3)Matches hex colors like #FF0000 or #F00
Understanding Flags
Case Insensitive (i)
Makes the pattern match regardless of letter case.
helloHello WORLD helloMultiline (m)
Makes ^ and $ match start/end of each line, not just the entire string.
^wordfirst line\nword at start\nlast lineDot All (s)
Makes the . character match newline characters as well.
start.*endstart\nmiddle\nendBest Practices
Do's
Test your patterns with various input examples
Use word boundaries (\b) instead of anchors for partial matches
Escape special characters when matching literally
Use non-capturing groups (?:) when you don't need the group
Keep patterns simple and readable
Don'ts
Avoid nested quantifiers like (.+)+ that cause backtracking
Don't use regex for parsing complex nested structures
Don't make patterns overly complex for simple tasks
Don't ignore case sensitivity requirements
Don't forget to test edge cases and empty inputs
Troubleshooting Common Issues
Pattern doesn't match anything
- • Check if you're using anchors (^ $) when you want partial matches
- • Verify your character classes and ranges are correct
- • Make sure special characters are properly escaped
- • Test with simpler versions of your pattern first
Pattern matches too much
- • Add word boundaries (\b) to prevent partial word matches
- • Use more specific character classes instead of . (dot)
- • Consider using non-greedy quantifiers (*? +? ??)
- • Add anchors if you need exact full-string matches
Performance warnings
- • Avoid nested quantifiers like (.*)+ or (.+)+
- • Use atomic groups or possessive quantifiers when possible
- • Keep alternation (|) options specific and ordered by likelihood
- • Consider breaking complex patterns into multiple simpler ones
Master Regular Expressions with Our Advanced Regex Tester
Test, debug, and perfect your regex patterns instantly with real-time matching, detailed analysis, and comprehensive pattern validation. Trusted by developers worldwide for accurate regex testing.
Why Choose Our Regex Testing Tool?
Instant Real-Time Testing
See matches, capture groups, and pattern behavior as you type. No delays, no page refreshes - just immediate feedback for faster development.
Advanced Pattern Analysis
Get detailed insights into pattern complexity, performance warnings, and optimization suggestions to write better regex expressions.
Safe and Secure Testing
Your patterns and test data never leave your browser. All processing happens locally for maximum privacy and security.
Perfect for Every Use Case
• Email Validation
• Form Input Validation
• Log File Parsing
• Data Extraction
• URL Pattern Matching
• Text Processing
• Search and Replace
• Code Analysis
• API Response Parsing
• Configuration Files
Common Regex Patterns Developers Need
Email Validation Regex
[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}Validates standard email addresses with proper domain structure and TLD requirements.
Phone Number Regex
\(\d{3}\)\s\d{3}-\d{4}Matches US phone numbers in (555) 123-4567 format with proper spacing and formatting.
URL Validation Regex
https?://[^\s]+Captures HTTP and HTTPS URLs from text, perfect for link extraction and validation.
IP Address Regex
((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]?)Validates IPv4 addresses with proper range checking for each octet (0-255).
Password Strength Regex
^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&])[A-Za-z\d@$!%*?&]{8,}Enforces strong passwords with uppercase, lowercase, numbers, and special characters.
Date Format Regex
\d{4}-\d{2}-\d{2}Matches ISO date format (YYYY-MM-DD) commonly used in databases and APIs.
Regular Expression Use Cases
Form Validation
Validate user input in real-time with custom regex patterns for emails, phones, and custom formats.
Data Extraction
Extract specific data patterns from logs, CSV files, and unstructured text efficiently.
Code Analysis
Parse source code, find patterns, and automate refactoring tasks with precise regex matching.
Log Processing
Parse server logs, extract error patterns, and monitor system health with regex-based filtering.
Start Testing Your Regex Patterns Now
Join thousands of developers who trust our regex tester for accurate pattern validation, debugging, and optimization. No signup required - start testing immediately.
Frequently Asked Questions About Regex Testing
What makes this regex tester different from others?
Our tool provides real-time pattern analysis, performance warnings, and detailed explanations of match behavior. Unlike basic testers, we show capture groups, execution time, and potential optimization issues to help you write better regex patterns.
Can I test complex regex patterns with multiple flags?
Yes, our tester supports case insensitive, multiline, and dot-all flags. You can combine multiple flags to test how your pattern behaves in different scenarios, with real-time updates showing exactly how flags affect matching behavior.
Is my test data secure when using this tool?
Absolutely. All regex testing happens locally in your browser - no data is sent to our servers. Your patterns and test text remain completely private and secure on your device.
How can I avoid catastrophic backtracking in my regex?
Our tool automatically detects potentially dangerous patterns that could cause catastrophic backtracking and warns you about them. We provide specific suggestions for optimizing your patterns to prevent performance issues in production.
Does the tool work with all programming languages?
Our regex engine follows standard PCRE (Perl Compatible Regular Expression) syntax, which is compatible with most modern programming languages including JavaScript, Python, PHP, Java, C#, and Go.