Regular Expression Generator

Create and test regular expressions with real-time feedback

Matches Found: 0

                            

                            

                                
Explanation

                                

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Mastering Regular Expressions: Complete Guide

                        
                        
Why Learn Regex?

                        

                            

                                
    
                                    
  • ⏱️ 10x faster text processing
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  • 🔍 90% of text operations covered
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  • 💻 Supported in all major languages
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Regex in Numbers

                                        
Used in 78% of production codebases

                                    

                                

                            

                        

    
                        
Performance Optimization

                        

                            

                                
                                    

                                        Technique
                                        Speed Gain
                                        Example
                                    

                                
                                
                                    

                                        Atomic Groups
                                        40% faster
                                        (?>pattern)
                                    

                                    

                                        Possessive Quantifiers
                                        30% faster
                                        a++
                                    

                                    

                                        Anchored Patterns
                                        2x faster
                                        ^start.*end$
                                    

                                
                            

                        

    
                        
Security Best Practices

                        

                            

                                

                                    

                                        
🛡️ ReDoS Prevention

                                        
    
                                            
  • Avoid nested quantifiers
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  • Set timeout limits
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🔐 Input Validation

                                        
    
                                            
  • Sanitize user patterns
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  • Use allow lists
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📚 Safe Patterns

                                        
    
                                            
  • Precompile static regex
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  • Limit backtracking
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Common Use Cases

                        

                            

                                

                                    

                                        
📧 Data Validation

                                        
/^[^\s@]+@[^\s@]+\.[^\s@]+$/

                                        
Email validation pattern

                                    

                                

                            

                            

                                

                                    

                                        
🌐 URL Parsing

                                        
/(https?:\/\/[^\s]+)/g

                                        
Extract URLs from text

                                    

                                

                            

                            

                                

                                    

                                        
🔢 Number Formatting

                                        
/\B(?=(\d{3})+(?!\d))/g

                                        
Add thousand separators

                                    

                                

                            

                        

    
                        
Regex Learning Path

                        

                            Pro Tip: Start with simple patterns and use online testers!
                        

                        
    
                            
  1. Basic syntax (^ $ . * + ?)
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  2. Character classes ([a-z], \d, \w)
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  3. Grouping and capturing
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  4. Lookaheads/lookbehinds
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  5. Performance optimization
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FAQ: Regular Expressions

                        

                            

                                

                                    
                                

                                

                                    

                                        .* is greedy (matches as much as possible), while .*? is lazy (matches as little as possible). Use lazy quantifiers to prevent over-matching.