The Selling Partner Appstore is an app marketplace run by Amazon. Businesses that sell on Amazon open it from Seller Central, the sellers' web console, to find applications that automate, manage and grow their selling. It lists apps made by Amazon and by third-party developers; Amazon's developer site counts more than 2,500 applications, 20+ countries and over 1.4 million sellers.
Apps are sorted into categories such as product research, listing, automated pricing, inventory and order management, shipping, advertising, accounting, analytics, taxes, funding and buyer messaging. Sellers search and filter, read ratings and reviews on each app's detail page, and connect an app through an OAuth authorization workflow (a standard way to give an app limited access to the seller account without sharing a password). Developers see app usage metrics on a dashboard.
To be listed, a developer must register a public SP-API application, set up the OAuth workflow and follow Amazon's Acceptable Use and Data Protection policies, then submit a listing form; the pages state no listing fee.