PayPal. SDKs and Downloads. Sample Code - IPN and APIs. Express Checkout - Button Code. PayPal requires that you use the following buttons and messages when implementing Express Checkout.
Please review the Express Checkout Integration Guide for complete instructions. Express Checkout Button. Getting Started With Express Checkout. The following list links to the integration guides for the PayPal NVP/SOAP APIs.
These integration guides do not include v.zero SDK and PayPal REST API integration details. For information on PayPal's more recently introduced API products, see all PayPal API docs. Alphabetical List of APIs and Tools Note: To view documentation for previous versions of PayPal products, see the Documentation Archive.