Regex Tester & Debugger
Test regular expressions in real-time with pattern matching, capture group visualization, and code generation
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Accepted: .txt,.log,.json,.md
Max size: 2 MB
Enter a regex pattern to start testing
- Enter a regex pattern to see explanation
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What is a Regex Tester?
A regex (regular expression) tester is an essential tool for developers that allows you to test, debug, and validate regex patterns in real-time. Regular expressions are powerful patterns used to match, search, and manipulate text in programming languages. Our regex tester provides instant feedback, highlighting matches and showing capture groups to help you perfect your patterns.
How to Use This Tool
- Enter your regex pattern in the pattern input field (without the surrounding slashes)
- Select flags like global (g), ignore case (i), or multiline (m) as needed
- Enter or paste your test string in the test string area
- View matches instantly with color-coded highlighting and detailed match information
- Explore capture groups to see what your regex is capturing
- Generate code in JavaScript, Python, PHP, Java, Ruby, or Go
- Load sample patterns to learn common regex patterns for emails, URLs, phone numbers, and more
Common Use Cases
- Email validation: Ensure email addresses match the correct format
- Phone number formatting: Extract and validate phone numbers in various formats
- URL extraction: Find and validate URLs in text content
- Data parsing: Extract specific data patterns from logs, CSV files, or API responses
- Input validation: Validate user input in forms (passwords, usernames, etc.)
- Text replacement: Find and replace patterns in large text documents
- Log file analysis: Parse and extract information from server logs
- Web scraping: Extract data from HTML or XML documents
Understanding Regex Syntax
Basic Syntax
\d- Matches any digit (0-9)\w- Matches word characters (letters, digits, underscore)\s- Matches whitespace (spaces, tabs, newlines).- Matches any character except newline^- Matches start of string$- Matches end of string
Quantifiers
*- Zero or more times+- One or more times?- Zero or one time (optional){'{n}'}- Exactly n times{'{n,m}'}- Between n and m times
Groups and Ranges
()- Capture group(?:)- Non-capturing group[]- Character set|- Alternation (OR)
Frequently Asked Questions
What regex flavors are supported?
Our regex tester primarily uses JavaScript regex engine for real-time testing. However, the code generator supports JavaScript, Python, PHP, Java, Ruby, and Go, with appropriate syntax adjustments for each language's regex implementation.
What do the regex flags mean?
g (global): Find all matches rather than stopping after the first match. i (ignore case): Make the pattern case-insensitive. m (multiline): ^ and $ match start/end of lines instead of entire string. s (dotall): . matches newline characters. u (unicode): Enable full Unicode matching. y (sticky): Match only from the exact position in the string.
How do I test multi-line regex patterns?
Enable the m (multiline) flag to make ^ and $ anchors match the start and end of each line instead of the entire string. This is useful when testing patterns across multiple lines of text.
Can I save and share my regex patterns?
Yes! Click the "Share URL" button to generate a shareable link that includes your regex pattern, flags, and test string. Anyone with the link can view and test your exact regex configuration. You can also use the "Generate Code" feature to export your regex pattern in your preferred programming language (JavaScript, Python, PHP, Java, Ruby, or Go).
Why isn't my regex pattern matching?
Common issues include: forgetting to escape special characters (use backslash \), not enabling the right flags (especially the global flag for multiple matches), incorrect quantifiers, or unmatched parentheses. Check the "Pattern Explanation" section for hints about your regex structure.
Are there keyboard shortcuts available?
Yes! Use Tab to navigate between buttons and text areas, Enter to activate focused buttons, and Escape while focused on text areas to quickly clear content.