Integration Guide

Table Of Contents
PayPal Payments Standard Integration Guide June 2012 317
7
Third-Party Shopping Carts – The
Cart Upload Command
Third-party shopping carts integrate PayPal Payments Standard on behalf of PayPal
merchants. Third-party carts use the Cart Upload command to pass the contents of shopping
carts to PayPal for checkout and payment processing.
NOTE: If you are not a shopping cart developer, you can add a PayPal Shopping Cart to your
site that is hosted by PayPal.
Read the following topics to learn more about third-party shopping carts:
“The Checkout Experience With the Cart Upload Command” on page 317
“Implementing the Cart Upload Command” on page 322
“Implementing the Instant Update API With the Cart Upload Command” on page 326
The Checkout Experience With the Cart Upload Command
The PayPal checkout experience with the Cart Upload command begins on a merchant's
shopping cart page, when someone clicks the check-out button. Alternatively, it begins when
someone selects PayPal on the merchant’s payment methods page.
The example below shows how a third-party shopping cart works with PayPal and PayPal
Payments Standard. The example merchant has the following account profile settings:
PayPal Account Optional is turned on – The buyer can pay without an existing PayPal
account and is offered the chance to sign up for one after completing the payment.
For more information, see “PayPal Account Optional” on page 356.
Shipping Calculations have been set up – PayPal calculates the shipping charges
automatically and adds them to the order.
For more information, see “Automatic Calculation of Shipping Charges (U.S. Merchants
Only)” on page 368 or “Automatic Calculation of Shipping Charges (non-U.S. Merchants
Only)” on page 384.
Auto Return is turned off – Buyers must click a Return to Merchant button to redirect
their browsers to the merchant website after completing their payments with PayPal.
For more information, see “Auto Return” on page 351.
What Buyers See With Third-Party Shopping Carts
Steve is shopping for photos on the Designer Fotos website. He selects several photos for
purchase by clicking the Add to Cart button underneath each one.