Regex Tester
Test and validate regular expressions with real-time matching, flags, and examples. Free online regex tester for developers and data analysts.
Enter a regex pattern and test string to see matches here.
Understanding Regular Expressions
Regular expressions (regex) are powerful tools for pattern matching and text processing. They are used in programming, data analysis, and system administration to search, validate, and manipulate strings. Regex syntax allows you to define complex search patterns using special characters, quantifiers, and character classes. Mastery of regex can greatly enhance productivity for developers, analysts, and anyone working with text data.
Regex is supported in most programming languages, including JavaScript, Python, Java, and more. Common use cases include input validation (emails, phone numbers), data extraction, search-and-replace operations, and log analysis. However, regex can be tricky to debug and maintain, so tools like this Regex Tester are invaluable for learning and troubleshooting.
This tool provides a safe environment to experiment with regex patterns, visualize matches, and understand how different flags affect results. Whether you are a beginner or an expert, practicing with real examples helps solidify your understanding and avoid common pitfalls.
How This Tool Works
The Regex Tester allows you to input a regular expression pattern, select flags (global, ignore case, multiline), and provide a test string. When you click "Test Regex," the tool compiles your pattern and applies it to the test string, displaying all matches and capture groups. The results section shows the matched text, its position, and any groups captured by parentheses in your pattern.
The tool uses JavaScript's built-in RegExp engine, so results are consistent with what you would see in web development or Node.js environments. Error handling is built-in: if your pattern is invalid, you'll receive a clear error message. You can also load example patterns for common use cases, making it easy to learn and experiment.
All processing happens locally in your browser for privacy and speed. No data is sent to any server, and you can safely test sensitive patterns or data.
Key Features
- Real-Time Testing: Instantly see matches and capture groups as you type your pattern and test string.
- Flag Support: Easily toggle global, ignore case, and multiline flags to see how they affect matching.
- Copy & Examples: Copy your regex pattern with one click, or load common examples for quick learning.
- Detailed Results: View all matches, their positions, and capture groups in a clear, organized format.
- Responsive Design: Works seamlessly on desktop (85% width) and mobile (95% width) for maximum usability.
- Privacy First: All processing is local; your data never leaves your device.
- Educational Content: Learn regex syntax, character classes, quantifiers, and more with built-in guides.
- Error Handling: Get instant feedback if your pattern is invalid or contains syntax errors.
- Accessibility: Designed for keyboard navigation and screen readers.
These features make the Regex Tester a must-have tool for developers, QA engineers, students, and anyone working with text data.
Common Use Cases
- Input Validation: Check if emails, phone numbers, URLs, or other user inputs match required formats.
- Data Extraction: Pull specific information from logs, documents, or web pages using capture groups.
- Search and Replace: Find and modify text in code, documents, or datasets efficiently.
- Syntax Highlighting: Power code editors and IDEs to highlight keywords, comments, and more.
- Log Analysis: Parse and analyze server logs, error messages, or system output for patterns.
- Web Scraping: Extract structured data from HTML or other text formats.
- Learning & Teaching: Practice regex skills or demonstrate concepts in classrooms and workshops.
- Security Audits: Identify patterns in code or data that may indicate vulnerabilities.
Regex is a universal tool for anyone dealing with text. This tester helps you master it for any scenario.
Step-by-Step Guide
- Enter Your Pattern: Type your regex pattern in the input box. Use /.../ syntax without the slashes.
- Select Flags: Toggle the global (g), ignore case (i), and multiline (m) flags as needed.
- Input Test String: Paste or type the text you want to test against your pattern.
- Click Test Regex: Press the button to see all matches and capture groups instantly.
- Review Results: Examine the matches, their positions, and any groups. Adjust your pattern or flags as needed.
- Try Examples: Load a quick example to see how common patterns work.
- Copy Pattern: Use the copy button to save your regex for use in code or documentation.
For best results, experiment with different patterns and flags. Use the educational content above to deepen your understanding of regex syntax and best practices.