How an Online Gift Card Checkout Works
When you use a gift card on an online purchase, the retailer's checkout processes it much like a debit card transaction. You enter the card number and, in most cases, the PIN on the back of the card. The system checks the balance and applies it to the order total.
The exact location of the gift card field varies between retailers. Most place it on the payment page as a separate "Gift Card" section, or fold it into a promo-code area. Account-based retailers may let you add a gift card to your wallet first and then apply it at checkout.
Store cards versus open-loop network cards online
A store-branded gift card only works on that retailer's site or app. A prepaid open-loop card carrying a Visa, Mastercard, AmEx, or Discover logo is entered like a regular credit card: card number, expiration date, CVV. Some open-loop cards need you to register a billing address before they can be used online.

