Regex Tester & Debugger

Write, test, and debug regular expressions in real-time. See instant match results and capture groups.

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About the Regex Tester

Our free online Regex Tester is an essential tool for developers to write, test, and debug Regular Expressions (Regex) in real-time. Whether you are validating email formats, extracting data, or replacing text, this tool makes working with regex simple and error-free.

How to Use

  1. Enter Pattern: Type your regular expression in the first input box.
  2. Set Flags: Add modifiers like g (global), i (case-insensitive), or m (multiline) in the small box next to it.
  3. Test String: Paste the text you want to search into the Test String text area.
  4. View Results: Matches and capture groups are instantly displayed below as you type.

Common Regex Flags

  • g - Global: Don't return after first match.
  • i - Case Insensitive: Case is ignored.
  • m - Multiline: ^ and $ match start/end of line.
  • s - Dot All: Allows . to match newline characters.

Frequently Asked Questions

What flavor of Regex does this tool use?

This tool runs directly in your web browser, so it uses the JavaScript (ECMAScript) regular expression engine. This means patterns that work here will work seamlessly in Node.js and browser-based applications.

Is my test data sent to a server?

No. All regular expression testing happens entirely client-side in your browser. Your regex patterns and test strings are never transmitted or stored, ensuring your data remains private and secure.

What are capture groups?

Capture groups are parts of a regex pattern enclosed in parentheses (...). They allow you to extract specific parts of a match, which is useful when parsing complex strings like URLs or log files. Our tool automatically displays all capture groups for each match.