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They most certainly do not have a singular canonical format. American Express cards use different groupings and a four-digit card security code.
by stonogo 11y ago
They most certainly do not have a singular canonical format. American Express cards use different groupings and a four-digit card security code.
- abhorrence 11y agoAt least for the US, the issuer of a credit card (and thus the format) can frequently be determined from as little as the first digit. For instance, nearly all card numbers starting with '4' are Visa.