Luhn Algorithm Validator — Free Online Tool
Validate any payment card number using the Luhn checksum algorithm. Auto-detects card type (Visa, Mastercard, Amex, Discover). Includes a collection of standard test card numbers for development testing. No real card data is stored or transmitted.
100% client-side. No uploads. Your data never leaves your browser.
How to use Luhn Algorithm Validator
- Paste a card number into the input field.
- The validator shows whether it passes the Luhn check and detects the card type.
- Switch to 'Test Cards' to copy standard test numbers for development.
- These numbers are Luhn-valid but not real card accounts.
Frequently Asked Questions
What is the Luhn algorithm?
A simple checksum formula used to validate identification numbers including credit cards. It catches common digit transposition errors.
Does a valid Luhn check mean it's a real card?
No. Luhn validation only checks the checksum. A valid Luhn number may not correspond to any real issued card.
Are these test cards safe to use?
Yes. These are well-known public test numbers (e.g. Stripe's test cards) that pass Luhn but are not real financial accounts.
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