Free Online Regex Tester & Validator — Test Regular Expressions Instantly

Welcome to Code Formatter's Regex Tester — the ultimate tool for testing, validating, and debugging regular expressions in real-time. Whether you're a seasoned developer building complex pattern matching systems or a beginner learning the fundamentals of regex, our free online regex tester provides instant visual feedback with highlighted matches, detailed match information, and a comprehensive library of common patterns.

Regular expressions (regex or regexp) are sequences of characters that define search patterns. They're a fundamental tool in programming, used for text validation, search and replace, and data extraction. Our regex tester eliminates the guesswork by showing you exactly what your pattern matches as you type. All processing happens 100% client-side in your browser, ensuring complete privacy.

How to Use Our Regex Tester

1. Enter Your Pattern: Type your regular expression in the pattern input field.
2. Select Flags: Click the flag buttons (g, i, m, s, u) to enable or disable modifiers.
3. Add Test String: Enter or paste the text you want to test. Matches are highlighted instantly.
4. Review Matches: The results panel shows all matches with their positions and captured groups.

Essential Regex Syntax Reference

• . — Matches any single character (except newline)
• * — Matches zero or more occurrences
• + — Matches one or more occurrences
• ? — Matches zero or one occurrence (optional)
• ^ — Matches the start of the string
• $ — Matches the end of the string
• [abc] — Matches any character in the brackets
• \d — Matches any digit
• \w — Matches any word character (letters, digits, underscore)
• \s — Matches any whitespace character

Common Regex patterns

For a complete lookup of common patterns including email, URL, and phone number validation, check our Regex Cheat Sheet. If you're building patterns for JavaScript, you might also find our JS Formatter useful.

Frequently Asked Questions

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