MyWebUtils: Free Online Dev Tools

What is a Regular Expression (Regex)?

A Regular Expression (or Regex) is a special sequence of characters that defines a search pattern. It's like a superpower for text searching, allowing you to find, match, and manipulate strings with incredible precision and flexibility. Regex is used in everything from form validation (e.g., checking if an email address is valid) to searching for complex patterns in large log files.

Why Do Developers Need a Regex Tester?

Writing regular expressions can be complex and tricky. A small mistake can lead to unexpected results or bugs. A Regex Tester provides a live, interactive environment to build and debug your patterns.

• Instant Feedback: See which parts of your text match your pattern in real-time as you type. Our tool highlights all matches, making it easy to see the effect of your changes.
• Debugging: Quickly identify why a pattern isn't working as expected. Is it a greedy quantifier? A forgotten escape character? The live preview helps you find the issue fast.
• Learning & Experimentation: A tester is the best way to learn regex. You can experiment with different tokens, flags, and character sets to understand their behavior without having to write and run a full script.
• Flag Control: Easily toggle common JavaScript flags like `g` (global, find all matches), `i` (case-insensitive), and `m` (multiline) to see how they affect the outcome.

How to Use This Tool

1. Enter Your Regex: Type your regular expression pattern in the input field at the top. You don't need to include the starting and ending slashes (`/`).
2. Select Flags: Use the checkboxes to enable or disable the `g` (global), `i` (case-insensitive), and `m` (multiline) flags.
3. Provide Test String: Paste or type the text you want to test your expression against in the "Test String" area.
4. Analyze the Results: The "Result" pane will instantly highlight all matching parts of your test string. The total number of matches is also displayed.