Quick Examples
Email Validation
[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}
Matches valid email addresses
Phone Number
\(?([0-9]{3})\)?[-. ]?([0-9]{3})[-. ]?([0-9]{4})
Matches US phone number formats
URL Matching
https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b([-a-zA-Z0-9()@:%_\+.~#?&//=]*)
Matches HTTP/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
RegEx Tips & Best Practices
Start Simple
Begin with basic patterns and gradually add complexity. Test each addition to ensure it works as expected.
Performance
Avoid excessive backtracking with quantifiers. Use atomic groups and possessive quantifiers when appropriate.
Escape Special Characters
Remember to escape special characters like . * + ? ^ $ { } [ ] \ | ( ) when you want to match them literally.
Readability
Use the x flag for complex patterns to add whitespace and comments for better readability.