Real-time testing, syntax explanation, common templates - demystifying regular expressions
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^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$
^1[3-9]\d{9}$
^https?:\/\/(www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b
^((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]?)$
^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])$
^#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3})$
^[a-zA-Z0-9_]{3,16}$
^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[@$!%*?&])[A-Za-z\d@$!%*?&]{8,}$
Regular expressions have a learning curve, but become very powerful once you master the basics. Start with simple patterns (like \d for digits, \w for word characters), then gradually learn quantifiers, groups, and assertions.
Simple regex patterns perform well, but complex nesting and backtracking can cause performance issues (ReDoS attacks). Tips: 1) Avoid excessive nesting; 2) Use non-capturing groups (?:...); 3) Test edge cases.
Use our tool for real-time testing! Enter your regex and test text to see match results. You can also use online visualization tools (like regex101.com) to view the matching process and explanations.
Common scenarios: 1) Form validation (email, phone); 2) Text search and replace; 3) Log analysis; 4) Data cleaning; 5) URL routing; 6) Syntax highlighting.