Regex Tester

What is Regex?

Regular expressions (regex) are powerful sequences of characters that define search patterns. They're used extensively in programming for text searching, validation, and manipulation. This tool helps you build, test, and debug regex patterns in real-time.

Our regex tester uses JavaScript's regex engine and supports all modern regex features including lookaheads, lookbehinds, capturing groups, and Unicode properties.

How to Use This Tool

1. Enter your regex pattern in the pattern input field
2. Select flags (g, i, m, s, u) as needed for your use case
3. Type or paste test text in the test string area
4. View results - matches are highlighted and detailed in the results panel
5. Use Replace mode to test substitutions with $1, $2 for groups

Common Regex Patterns

• ^ - Start of string/line
• $ - End of string/line
• . - Any character except newline
• \d - Any digit (0-9)
• \w - Any word character (a-z, A-Z, 0-9, _)
• \s - Any whitespace character
• [abc] - Any character in the set
• [^abc] - Any character not in the set
• a* - Zero or more of 'a'
• a+ - One or more of 'a'
• a? - Zero or one of 'a'
• a{3} - Exactly 3 of 'a'
• (abc) - Capturing group
• (?:abc) - Non-capturing group