When you are asked to input your card information online, how is it that some websites can automatically know if you input an invalid number and others cannot, before payment is processed?Example: as soon as I typed the last number of my card wrong, it went red and would not allow me to continue before I corrected it.
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TMI About Credit Card Numbers
There’s actually a ton of information contained in a credit card number. This information isn’t really necessary for understanding how to use a credit card, it’s just here so you can learn for fun. The ISO or the International Organization for Standardization categorizes the numbers like so:
Digits 1 – 6: Issuer identifier numbers
First digit: Represents the network that produced the credit card. It is called the Major Industry Identifier (MII). Each digit represents a different industry.
0: ISO/TC 68 and other industry assignments
1: Airlines
2: Airlines, financial and other future industry assignments
3: Travel and entertainment
4: Banking and financial
5: Banking and financial
6: Merchandising and banking/financial
7: Petroleum and other future industry assignments
8: Healthcare, telecommunications and other future industry assignments
9: For assignment by national standards bodies
The first digit is different for each card network:
Visa cards begin with a 4 and have 13 or 16 digits
Mastercard cards begin with a 5 and has 16 digits
American Express cards begin with a 3, followed by a 4 or a 7 has 15 digits
Discover cards begin with a 6 and have 16 digits
Diners Club and Carte Blanche cards begin with a 3, followed by a 0, 6, or 8 and have 14 digits
Digits 2 – 6: Provide an identifier for a particular institution
Digits 7 – 15: Unique personal identifiers
Identify the cardholder name
Unique to the issuer
Digit 16: Check digit
This last digit verifies card numbers for accuracy to make sure that they weren’t input incorrectly
The rest of the digits are also different for each card network:
Visa cards:
Digits 2 – 6: Make up the bank number
Digits 7 – 12 or 7 – 15: Represent the account number
Digits 13 or 16: Is a check digit
Mastercard cards:
Digits 2 & 3, 2 – 4, 2 – 5, or 2 – 6: Make up the bank number; depends on whether digit two is a 1, 2, 3 or other digit
Digits after the bank number, up to digit 15: Represent the account number
Digit 16: Is a check digit
American Express cards:
Digits 3 & 4: Are type and currency
Digits 5 – 11: Represent the account number
Digits 12 – 14: Represent the card number within the account
Digit 15: Is a check digit
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