Credit card security codes of different banks are printed in different places. The card security codes of UnionPay cards, MasterCard cards, VISA cards and JCB cards in most banks are all three digits, which are generally printed in the last three digits of the signature column on the back of the card.

Credit card security codes can generally be used to verify credit card transactions, as important as passwords. Even some websites do not need to provide a password, just provide the credit card number, expiration date and security code.