Amazon Marketplace Web Service (Amazon MWS) is an integrated Web service API that helps Amazon sellers to programmatically exchange data on listings, orders, payments, reports, and more. XML data integration with Amazon enables higher levels of selling automation, which helps sellers grow their business. By using Amazon MWS, sellers can increase selling efficiency, reduce labor requirements, and improve response time to customers.

Amazon MWS supports seller API functions that are broader in scope and functionality than any API functionality previously offered to sellers by Amazon. With Amazon MWS, Amazon listing, order, and payment data can be integrated into existing workflows so that selling on Amazon fits seamlessly with sellers' current business practices.

The Amazon Marketplace Web Service (Amazon MWS) Fulfillment API sections include operations that allow sellers to access Amazon's world-class Fulfillment capabilities through a simple Web services interface. Among other features, a seller can programmatically send order information to Amazon with instructions to fulfill customer orders on the seller's behalf.

Sellers registered for Fulfillment by Amazon (FBA) send inventory to Amazon's fulfillment centers. When orders are placed on the Amazon site, or when a seller sends order information for orders placed through another sales channel, Amazon will pick, pack, and ship the products to the seller's customers. FBA frees sellers from having to manage the order fulfillment process, while still allowing sellers to maintain control over their inventory. The Amazon MWS Fulfillment functionality extends the benefits of FBA by allowing sellers to integrate FBA capabilities directly into their own Web sites or other sales channels. Sellers can more efficiently create and send inbound shipments of inventory to Amazon's warehouses and instruct Amazon to fulfill customer orders, creating a nearly virtual business. There is no additional charge for using the Amazon MWS Fulfillment functionality; only fees for the underlying FBA and selling services apply.

With the Amazon MWS Fulfillment operations, sellers can directly integrate their systems with the FBA systems to more efficiently create and send shipments to Amazon and automatically send order information to Amazon for orders placed on non-Amazon sales channels. This functionality is contained in three key API sections: Fulfillment Inbound Shipment, Fulfillment Outbound Shipment, and Fulfillment Inventory.