Credit card security codes are vital to keeping your online and phone transactions safe. This three or four-digit number is hidden behind the cardholder's signature area. The specific location varies depending on the card type. For example: The security code of a VISA card is usually printed on the three digits at the end of the card number in the signature line. The MasterCard security code is also three digits at the end of the card number in the signature field. The security codes for Discover cards and UnionPay cards are located in the same position in the signature field, immediately following the end of the card number. The security code for your American Express card is located on the front of the credit card, above the card number. The security code of the JCB card is also at the end of the signature field, but behind the card number.

The design principle of the security code is to generate it through the bank's encryption of card information. Only the issuing bank and the cardholder know its specific value, ensuring identity verification during the payment process. So, next time you use your credit card, be sure to pay attention to this secret number to ensure a safe transaction.

Reference material: Credit card security code