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Regex Tester

Test and debug regular expressions with live matching, group extraction, and detailed explanations. All processing happens locally in your browser for maximum privacy and security.

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Enter a regex pattern to start testing

Understanding Regular Expressions

What are Regular Expressions?

Regular expressions (regex) are powerful patterns used to match and manipulate text. They provide a concise and flexible means to identify strings of text, such as particular characters, words, or patterns of characters.

Example: \d3-\d3-\d4 matches phone numbers like 555-123-4567

Why Use This Tool?

Testing regex patterns can be tricky. This tool provides real-time feedback, highlighting matches in your test text, showing capture groups, and helping you debug complex patterns before implementing them in your code.

Key Features:

  • • Live pattern matching
  • • Capture group visualization
  • • Common pattern library
  • • Flag support (global, case-insensitive, etc.)

Common Use Cases

Data Validation

Validate user input like email addresses, phone numbers, postal codes, and credit card numbers in forms and applications.

Text Processing

Extract specific information from large text files, logs, or documents. Parse structured data and transform text formats.

Search & Replace

Perform complex find and replace operations in code editors, databases, and content management systems.

URL Routing

Define flexible URL patterns in web frameworks to match different route structures and extract parameters.

Best Practices

Start Simple

Begin with basic patterns and gradually add complexity. Test each addition to ensure it works as expected.

Use Non-Capturing Groups

When you need grouping but don't need to capture the matched text, use (?:) to improve performance.

Be Specific

Avoid overly broad patterns that might match unintended text. Use character classes and anchors appropriately.

Test Thoroughly

Test your patterns with various inputs, including edge cases and invalid data to ensure robustness.

Document Complex Patterns

Add comments to explain complex regex patterns in your code. Future you (and your team) will thank you.

Common Patterns

Email Validation

[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}

Matches most common email address formats

Phone Number (US)

\(?\d{3}\)?[-.\\s]?\d{3}[-.\\s]?\d{4}

Matches US phone numbers in various formats

URL/Website

https?://[^\s]+

Simple pattern for HTTP/HTTPS URLs

Hexadecimal Color

#(?:[0-9a-fA-F]{3}){1,2}\b

Matches 3 or 6 digit hex color codes