Most of us use credit cards regularly, but very few know how these cards actually work. Recently, a software engineer and online shopping enthusiast shared an X (formerly Twitter) thread explaining the science behind credit card numbers. Alongside this, FinPal also posted how e-commerce platforms like Amazon and Flipkart instantly verify whether a card is valid and what offers are linked to it.

Credit Card Numbers Are Not Random

FinPal explained in a conversation with ET Wealth Online that credit card numbers are generated using a hidden algorithm. This ensures quick validation and smoother banking transactions.

How Is a Credit Card Number Validated?

Banks use the Luhn Algorithm to verify whether a card number entered by the user is valid.

• In this method, every alternate digit of the card number is doubled.

• All the resulting digits are then added together.

• If the final sum is divisible by 10, the card number is considered valid.

This quick mathematical check allows e-commerce portals to instantly identify invalid numbers.

The Role of BIN (Bank Identification Number)

The first 6 to 8 digits of a credit card are called the Bank Identification Number (BIN).

• BIN tells the system which bank issued the card.

• Using this, portals can identify whether your card belongs to Visa, Mastercard, RuPay, etc.

• It also helps platforms like Amazon and Flipkart determine what bank-specific offers or discounts are available on your card.

How Is the Card Network Identified?

• The first digit of a card number is called the Major Industry Identifier (MII). It identifies the network (Visa, Mastercard, RuPay, etc.).

• The first 6–8 digits (BIN) further specify the issuing bank and card type (for example, HDFC Infinia, SBI Elite, etc.).

This system allows merchants to validate cards instantly, reduce fraud, and apply bank offers automatically.