Regex Tester

What is a Regular Expression?

A regular expression (regex or regexp) is a pattern of characters that defines a search pattern. It's used to match, find, and replace text in strings. Regular expressions are powerful tools in programming and text processing, supported by most modern languages.

Key Features

• Global Flag (g) — Find all matches instead of just the first one
• Case Insensitive (i) — Match uppercase and lowercase letters as equivalent
• Multiline (m) — Treat ^ and $ as line boundaries, not string boundaries
• Dotall (s) — Make . match newline characters
• Capture Groups — Use parentheses to extract parts of matched text

Common Patterns

• \d+ — One or more digits
• [a-z]+ — One or more lowercase letters
• \S+ — One or more non-whitespace characters
• (\w+)@(\w+) — Email pattern with capture groups