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Regular Expression (RegEx) Tester

Test regular expressions against text in real-time with syntax highlighting, capture groups, and flag support.

Regular Expression Tester

Write, test, and debug your regex patterns in real-time against sample text directly in your browser.

/
/g
Waiting for input...
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What is Regular Expression (RegEx) Tester?

A Regular Expression (Regex or RegExp) is a powerful sequence of characters that forms a search pattern. They are used extensively in programming and text processing to search, match, and manipulate strings based on complex criteria. For instance, you can use regex to validate email addresses, extract phone numbers from a document, or replace specific formatting in code. Because the syntax can be dense and unintuitive, having a live visualizer is essential for debugging.

Common Use Cases

  • Validating user input in web forms (passwords, emails, phone numbers).
  • Parsing logs to find specific error codes or timestamps.
  • Extracting structured data from messy, unstructured text files.

Example: Input & Output

Sample Input

See the tool above for interactive examples.

Expected Output

The processed output will appear here instantly.

How to Use

  1. Step 1: Enter your regular expression pattern in the top input box.
  2. Step 2: Type or paste the target string you want to search into the test text area.
  3. Step 3: Adjust your flags (like global 'g' or case-insensitive 'i') as needed.
  4. Step 4: Matches and capture groups will be highlighted immediately.

Frequently Asked Questions

What regex engine does this use?

This tool runs using the JavaScript regex engine built into your web browser.

Can I use lookbehinds?

Yes, modern browsers support both lookaheads and lookbehinds in JavaScript regular expressions.

Is my data secure?

Yes. Everything is processed locally in your browser. No data is sent to our servers.

Privacy & Security

All data processing for the Regular Expression (RegEx) Tester happens entirely on your local machine within your browser. No data is ever sent to our servers, ensuring your information remains private and secure. We believe in privacy by design, and our tools are built to be used without compromising your data.