What is a BIN (Bank Identification Number)?

bank i - dent - i - fi - ca - tion num - ber
The first four to six digits on a credit card, which can be used to identify the Issuing Bank that issued the card.
How Does a Bank Identification Number Work?

The first section of the Bank Identification Number identifies the location of the bank that issued the card, while the latter portion identifies the specific name of the bank. BINs are traditionally used by online Merchants as a way to detect fraud by matching the geographic area where the cardholder is located to the geographic area identified in the Bank Identification Number. The term Issuer Identification Number (IIN) and Interbank Card Association Number (ICA) also refer to this same collection of numbers. A personal identification number, or PI identifies a cardholder.

For more information, read "The Payments System Simplified"
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