Regex Tester

Regular Expressions - A Powerful Pattern Matching Tool

Regular expressions (regex) are sequences of characters that define a search pattern. They are widely used for string matching and manipulation in programming, text editors, and command-line utilities.

Common Regex Patterns

• ^ - Matches the beginning of a string
• $ - Matches the end of a string
• . - Matches any single character except newline
• * - Matches 0 or more occurrences of the preceding element
• + - Matches 1 or more occurrences of the preceding element
• ? - Matches 0 or 1 occurrence of the preceding element
• \d - Matches any digit (0-9)
• \w - Matches any word character (a-z, A-Z, 0-9, _)
• \s - Matches any whitespace character
• [abc] - Matches any one of the characters a, b, or c
• [^abc] - Matches any character except a, b, or c
• (x|y) - Matches either x or y

Common Use Cases

• Email Validation: ^[\w.-]+@[\w.-]+\.\w+$
• URL Validation: ^(https?:\/\/)?([\da-z\.-]+)\.([a-z\.]{2,6})([\/\w \.-]*)*\/?$
• Phone Number: ^\(?(\d{3})\)?[- ]?(\d{3})[- ]?(\d{4})$
• Date (MM/DD/YYYY): ^(0[1-9]|1[0-2])\/(0[1-9]|[12]\d|3[01])\/\d{4}$
• Password Strength: ^(?=.*[A-Za-z])(?=.*\d)[A-Za-z\d]{8,}$ (at least 8 characters, one letter and one number)

Tips for Writing Effective Regular Expressions

1. Start simple and build complexity gradually.
2. Test your regex with various inputs, including edge cases.
3. Use capturing groups to extract specific parts of a match.
4. Be careful with greedy quantifiers (* and +) as they match as much as possible.
5. Consider using non-greedy quantifiers (*? and +?) for more controlled matching.
6. Comment complex regexes for better maintainability.