About Regex Tester
Regular expressions are one of the most powerful tools in a developer's toolkit, but they can also be notoriously difficult to get right. Our Regex Tester provides a real-time environment where you can write a pattern, supply test text, and instantly see every match highlighted in place. Capture groups, named groups, and match indices are displayed in a detailed breakdown below the highlighted output, so you never have to guess what your pattern actually matches.
How to Use
Enter your regular expression in the pattern field. Use the checkboxes to toggle flags such as global (g), case-insensitive (i), multiline (m), and dotall (s). Type or paste your test string, and matches appear highlighted in real time. Click Common Patterns to open a library of pre-built expressions for emails, URLs, phone numbers, IP addresses, dates, and more. Selecting a pattern inserts it into the pattern field with the appropriate flags.
Key Features
- Live matching with color-coded highlights directly in the test string.
- Detailed match information including index, length, and capture groups.
- Flag toggles for global, case-insensitive, multiline, and dotall modes.
- Built-in library of 12+ common patterns for quick insertion.
- Clear error messages when a pattern contains syntax mistakes.
- Runs entirely in your browser with no data sent to any server.
Common Use Cases
Regex testers are invaluable for form validation, log parsing, data extraction, search-and-replace operations, and building text processors. Whether you are crafting a pattern to validate email addresses, extract data from CSV files, or sanitize user input, a live tester lets you iterate much faster than running your code repeatedly. The common patterns library also serves as an educational resource for learning regex syntax.