Regex Tester
Test regular expressions with real-time matching and highlighting. See matches instantly as you type.
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What is a Regular Expression?
A regular expression (regex) is a sequence of characters that defines a search pattern. They are used for pattern matching in strings, validation, search and replace operations, and data extraction.
Regex Flags
- g (Global): Find all matches rather than stopping after the first match.
- i (Case Insensitive): Match letters regardless of case.
- m (Multiline): ^ and $ match the start/end of each line, not just the string.
- s (Dot All): The dot (.) matches newline characters.
- u (Unicode): Treat the pattern as a sequence of Unicode code points.
Common Regex Patterns
- \d - Match any digit (0-9)
- \w - Match any word character (letters, digits, underscore)
- \s - Match any whitespace
- . - Match any character (except newline by default)
- * - Match 0 or more of the preceding element
- + - Match 1 or more of the preceding element
- ? - Match 0 or 1 of the preceding element
- ^ - Match the start of the string
- $ - Match the end of the string
Use Cases
- Form Validation: Validate email addresses, phone numbers, URLs
- Data Extraction: Extract specific patterns from text
- Search & Replace: Find and replace patterns in code editors
- AI Prompt Engineering: Parse and validate AI model outputs
- Log Analysis: Extract timestamps, IPs, and error codes from logs