Software engineer explains how online portals instantly check if a credit card number is valid and bank specific offers are instantly applied

FinPal, a software engineer, explained on X how online portals instantly validate credit card numbers using the Luhn Algorithm and apply bank-specific offers through the BIN system. The first digit identifies the card network, while the initial 6-8 digits reveal the issuing bank and card type. RBI guidelines address unsolicited cards, activation criteria, and interest charges on partial payments.