Credit Card Validator (Luhn Algorithm Check)

Validate payment card numbers using the standard ISO/IEC 7812 Luhn checksum algorithm, detect card issuers (BIN check), and inspect step-by-step arithmetic.

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100% Client-Side Privacy Guaranteed: All card verification runs locally inside your browser memory. No card number is ever stored, logged, or transmitted over any network. Designed for testing e-commerce integrations and sandbox numbers.

Payment Sandbox Test Cards:

Enter Card Number (Digits or Formatted)

✓

Valid Card Number (Luhn Passed)

Issuer: Visa • Length: 16 digits • Luhn Sum Mod 10: 80 % 10 = 0

Visa

4242 4242 4242 4242

Cardholder

SANDBOX TEST USER

LUHN OK

Step-by-Step Luhn Algorithm Checksum Table

From right to left, every second digit is doubled. If doubling yields a number greater than 9, its digits are added together (or 9 is subtracted). If the sum of all resulting numbers is a multiple of 10 (`sum % 10 === 0`), the card checksum is valid.

Position (Right to Left)	Original Digit	Doubled (Even Pos)	Digit Contribution
Pos #1 (Check Digit)	2	—	+2
Pos #2	4	4 × 2 = 8	+8
Pos #3	2	—	+2
Pos #4	4	4 × 2 = 8	+8
Pos #5	2	—	+2
Pos #6	4	4 × 2 = 8	+8
Pos #7	2	—	+2
Pos #8	4	4 × 2 = 8	+8
Pos #9	2	—	+2
Pos #10	4	4 × 2 = 8	+8
Pos #11	2	—	+2
Pos #12	4	4 × 2 = 8	+8
Pos #13	2	—	+2
Pos #14	4	4 × 2 = 8	+8
Pos #15	2	—	+2
Pos #16	4	4 × 2 = 8	+8
Total Luhn Checksum:			80 (Mod 10 = 0)