Regex Tester

Regular expressions (regex or regexp) are powerful patterns used to match, search, and manipulate text. They are supported in virtually every programming language including JavaScript, Python, Java, PHP, and more. From validating email addresses to parsing log files, regex is an indispensable skill for any developer.

Common Regex Syntax

Key regex elements include: \d (digits), \w (word characters), \s (whitespace), . (any character), * (zero or more), + (one or more), ? (optional), [] (character classes), () (groups), ^ (start), and $ (end). Combine these building blocks to create patterns that match exactly the text you need. For example, \b\w+@\w+\.\w+\b matches simple email-like patterns.

Tips for Writing Better Regex

Start simple and build up complexity. Test frequently with real sample data. Use non-greedy quantifiers (*? and +?) when you want the shortest possible match. Use named groups (?...) for readability. Avoid catastrophic backtracking by being specific with your patterns — use character classes [] instead of . when possible, and anchor your patterns with ^ and $ when appropriate.