Regex Tester

Professional regex testing for developers and programmers. Test and validate regular expressions with real-time matching and detailed analysis.

🔍 Real-time Testing: Test regex patterns instantly with live matching, flags support, and detailed match information. Perfect for debugging and validating complex patterns.

Test Your Regular Expression

Input Configuration

Enter your regular expression pattern with proper escaping
Supported: i (ignore case), m (multiline), s (dotall)
Paste or type the text you want to test your regex pattern against

Test Results

Ready to Test

Enter a regex pattern and test string to see matches here.

About Regular Expressions

What are Regular Expressions?

Regular expressions (regex) are powerful patterns used to match, search, and manipulate text. They provide a concise way to describe complex text patterns and are supported by most programming languages and text editors.

Common Regex Flags

i (ignore case): Case-insensitive matching
m (multiline): ^ and $ match line boundaries
s (dotall): . matches newlines
g (global): Find all matches (not just first)

Why Test Regex?

Validation
Debugging
Learning
Optimization

How to Use This Tool

  1. Enter your regex pattern in the pattern field
  2. Add any flags if needed (i, m, s)
  3. Enter test text in the test string field
  4. Click "Test Regex" to see matches
  5. Review match details and positions

Regex Examples:

Email: [\w\.-]+@[\w\.-]+\.\w+
Phone: \(\d{3}\) \d{3}-\d{4}
URL: https?://[^\s]+
Date: \d{2}/\d{2}/\d{4}

Regex Metacharacters

Anchors: ^ (start), $ (end), \b (word boundary)
Quantifiers: * (0+), + (1+), ? (0-1), {n,m}
Character Classes: [abc], [^abc], \d, \w, \s
Groups: (abc), (?:abc), (?abc)
Alternation: a|b|c

Key Features

Real-time Testing
Multiple Flags
Detailed Info
Copy Matches
Free to Use
Position Tracking

Regex Applications

Programming

Validate user input, parse data, search and replace text, and extract information from strings in code.

Data Processing

Extract emails, phone numbers, URLs, and other patterns from large datasets and text files.

Text Editing

Find and replace patterns in text editors, perform bulk operations, and automate text transformations.

Frequently Asked Questions

This tool uses Python's built-in re module, which implements a regular expression engine compatible with Perl-style regex. It supports most common regex features and flags used in programming languages like Python, JavaScript, Java, and PHP.

The tool supports the most commonly used regex flags: i (ignore case for case-insensitive matching), m (multiline mode where ^ and $ match line boundaries), and s (dotall mode where . matches newlines). These flags can be combined (e.g., "im" for case-insensitive multiline mode).

Common reasons for invalid regex patterns include: unescaped special characters (like parentheses, brackets, or dots), mismatched parentheses or brackets, invalid quantifiers (like {5,3} where the minimum is greater than maximum), or unsupported syntax. Try escaping special characters with backslashes or check your parentheses/brackets matching.

Regex matching works by trying to find substrings in your test text that match the pattern you specified. The engine starts from the beginning of the text and tries to match your pattern. If it finds a match, it records the match and continues searching (unless you have specific flags that change this behavior). Each match includes the matched text and its position in the original string.

Yes, your privacy is completely protected. All regex processing happens locally in your browser. Your patterns and test text never leave your device or get stored on any server. This ensures complete privacy and security for your regex testing needs.

Ready to Test Your Regular Expressions?

Start testing and validating your regex patterns instantly. No registration required, completely free, and secure.

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Regex Tester Keywords

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