Card Number Validator
Validate credit card numbers using the Luhn algorithm, detect card networks, and verify number length. Everything runs client-side - no data leaves your browser.
Card Network Detection Rules
| Network | Prefix(es) | Length |
|---|---|---|
Visa | 4 | 13, 16, 19 |
Mastercard | 51-55, 2221-2720 | 16 |
Amex | 34, 37 | 15 |
Discover | 6011, 644-649, 65 | 16-19 |
JCB | 3528-3589 | 16-19 |
Diners Club | 36, 38, 300-305 | 14-19 |
UnionPay | 62 | 16-19 |
Maestro | 5018, 5020, 5038, 6304, 6759, 6761-6763 | 12-19 |
What is the Luhn Algorithm?
The Luhn algorithm (also called mod-10) is a checksum formula used to validate identification numbers such as credit card numbers. It detects single-digit errors and most transpositions of adjacent digits.
Client-Side Only
This tool runs entirely in your browser. No card numbers are transmitted to any server. Your data stays on your device and is never stored or logged anywhere.
Payment Recovery
Invalid card numbers are a common source of payment failures. Validating numbers before processing helps catch typos and formatting issues that lead to unnecessary declines.
Reduce Payment Failures
Slicker uses intelligent retry logic to recover failed payments at the optimal time. By analyzing card data, decline codes, and hundreds of other signals, Slicker maximizes recovery rates while minimizing customer friction.
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