Credit Card Validator
Validate credit card numbers using the Luhn algorithm and detect card types.
Test numbers: 4242424242424242 (Visa), 5555555555554444 (Mastercard), 378282246310005 (Amex)
About the Luhn Algorithm
The Luhn algorithm (also known as the "modulus 10" or "mod 10" algorithm) is a simple checksum formula used to validate identification numbers such as credit card numbers. It was created by IBM scientist Hans Peter Luhn. Most credit card numbers are generated following this specification.
How to Use Credit Card Validator
- Paste your code or data into the input field
- Choose the operation you want to perform
- View the formatted, validated, or transformed output
- Copy the result or download if available
Why Use Credit Card Validator?
Developer tools on FreeTools.one are designed to replace the dozen browser tabs you'd otherwise need. JSON formatting, regex testing, JWT decoding, SQL formatting, diff checking — everything runs in your browser with zero configuration. There's nothing to install, no CLI to learn, no Docker containers to spin up. Each tool provides professional-grade output with syntax highlighting, error detection, and one-click copy. Your code and data never leave your device because all processing happens client-side. These tools are built by developers, for developers, with the exact features you need: customizable indentation, multiple output formats, real-time validation, and keyboard shortcuts. They're fast enough for quick checks during coding sessions and powerful enough for production data transformation.
- No installation needed — works directly in your browser
- Client-side processing keeps your code private
- Professional-grade formatting and validation
- Save hours of manual coding and debugging
Frequently Asked Questions
Is my code sent to a server?
No. All processing happens in your browser. Your code never leaves your device.
Does it support syntax highlighting?
Yes. Output is displayed with proper formatting for easy reading.
Can I use this for production code?
Absolutely. The output is clean and ready for production use.