Application Programming Interfaces, or APIs, drive the modern web in ways that are not always obvious to the end user. APIs connect different systems to enable rich experiences. Some of these connections are evident on the surface level, as APIs provide much of the content and login flows that users experience on a daily basis.

One of the most important ways APIs are utilized is within partner ecosystems. Partner APIs are quite common. In fact, 27% of APIs are partner APIs, or those APIs shared only with integration partners, according to the 2022 Postman State of API Report.

Still, most users don’t realize a partner API is driving many everyday web experiences, like eCommerce or travel booking. So what is a partner API? What do these APIs functionally do? And what are some good examples? Below, we’ll define what partner APIs are and examine six examples of partner APIs in practice.

What Is a Partner API?

Generally speaking, web APIs can be classified into three distinct types: public, private, and partner.

Public APIs are publicly accessible and either open or productized with a freemium structure. Public APIs are highly visible by their very nature, and as such, are the APIs most common users think about when they consider APIs. Private APIs are the exact opposite, forming an internal backbone and structure to data systems. These APIs are typically more purpose-built for a specific company, and you’re unlikely to interact with them unless you’re working on an internal service.

Partner APIs, however, occupy a strange middle ground. They are meant to be public, but only for specific, approved consumers. Partner APIs interact with internal services in such a way that they can be considered distinct from private APIs. For these reasons, partner APIs are often the unsung heroes of the API space.

Six Examples of Partner APIs

Now that we know what a partner API actually is, let’s look at some great examples in the market.

1. Amazon Selling Partner API

Amazon’s Selling Partner API, or SP-API, is a RESTful API designed to connect partners who sell on Amazon to the backend services that power the ordering, payment, and shipping processes underpinning the eCommerce platform.

According to Amazon, the SP-API can “increase selling efficiency, reduce labor requirements, and improve response time to customers, helping selling partners grow their businesses.” Beyond the eCommerce systems the API provides, SP-API also provides substantial security and compliance verification through SP-API Guard, a robust Sandbox for application testing, a Health Dashboard for health status reporting of services, an SDK for application creation and testing, and much more.

Notably, the SP-API also provides an OAuth authorization flow for selling partners, which allows for the connection of an external store to the internal systems, making all of these tools and their adoption relatively seamless for adopting partners.

The importance of this API can’t be overstated. Amazon’s global presence drives much of the online shopping experience of the average user. This partner API is responsible for how Amazon shopping functions from a B2B point of view. If you have bought something from Amazon in the past year, chances are you have benefited directly from this API, even if the API itself was essentially invisible.

2. Airbnb Partner API

The Airbnb Partner API is interesting in that you don’t contact Airbnb and apply — they contact you and ask for integration. For this reason, the API is generally closed off except for their closest integration partners. That being said, it still provides quite a lot of functionality that improves the Airbnb user platform.

Principally, the Airbnb API is designed to connect multiple listings and booking systems to an Airbnb. Some of Airbnb’s expansion in the last few years has been through the addition of smaller hotels, hostels, and other lodging services on the platform as an effort to increase supply.

While this makes sense from a practical point of view, the old Airbnb approach of tying these properties to individual management screens means that someone running a 12-room hostel might struggle with the system and opt not to include the supply. Without integration, third parties might view Airbnb as a competitor rather than a tool that could boost revenue.

The Airbnb API provides this functionality, connecting the management of properties to customer data in a seamless way with external management, booking, and reporting systems.

3. eBay APIs

The eBay Partner API fills a specific niche need for partners — the ability to engage in affiliate marketing, buying, and selling with the eBay platform in connection to their own systems. The “Partner API” is really a very thin additional step when accessing the standard eBay API. Instead of providing a whole secondary Partner API, each call made through the Partner system is given a unique partner Campaign ID which ties the actions on that API to the partner in question.

What this looks like in practice is that a Partner, once accepted into the program, is given a unique campaign ID that is used to trigger a Partner API connection. From here, all of the eBay APIs, including the Buy API, Sell API, Commerce API, and Developer API, are surfaced to the partner. When an action is taken on one of those APIs, the Campaign ID is appended, allowing partner functionality — such as connecting analytics to campaigns or running affiliate marketing — to be properly credited to the partner.

This is a great way to enable partner-only perks without refactoring an existing platform. Once the API is created, anyone can, in theory, use it, but a partner can claim specific features by using the Partner API Campaign ID.

4. Skyscanner Travel API

Skyscanner’s Partner API, called Travel API, is an excellent example of porting a first-party experience to third-party solutions. The API, in this case, literally mirrors the functionality of the primary Skyscanner experience through third-party websites or applications, connecting external customers to the Skyscanner service that might otherwise use a competitor or external system.

Notably, Skyscanner is not a single service provider. Skyscanner notes in its documentation that it not only allows, but expects, partners to combine the Skyscanner suite with existing travel systems to help deliver the best deals to the end user. This makes the Skyscanner API an additive tool.

Skyscanner also provides quite a lot of additional service functionality through the use of its Support Network. The Support Network includes an account manager, engineering support, and much more, meaning that partner efforts are not done in isolation. Instead, Skyscanner provides ample support to leverage and extend inclusion throughout the system to deliver greater integration and success.

5. Shutterstock Partner Solutions

The Shutterstock partner API is perhaps the most widely adopted API discussed in this piece. The service is used by companies like Google, Apple, Microsoft, and IBM for various projects. The concept is simple — the Shutterstock API connects partners to millions of royalty-free images, videos, and music tracks, and provides a dedicated partner and integration support apparatus to facilitate these connections.

Where the Shutterstock API comes into its own is the unique applications that utilize the content. Partners have taken this media and done some amazing things with it:

• Apple uses the media provided by Shutterstock as part of its video production flow.
• Magic Leap uses Shutterstock content to create mixed reality projects for their consumer base.
• Wix.com provides content for website creation, lowering the barrier of entry and decreasing the time to production for their website builder.
• Art.com connects Shutterstock images to collection curation to provide users with gorgeous content.

This is just the tip of the iceberg, of course. Everything from training computer vision on data sets to AI-powered visual search could be enabled through this service.

6. Kroger Partner API

This particular API is an excellent example of a partner API arising from a business need. The Kroger Partner API is, in a way, a shim API between brands. While the API does everything you would expect a grocery giant’s API to do, connecting customer data to shopping habits and commerce information, the key with the Kroger Partner API is that this data is connected between all its brands.

The Kroger Partner API connects many brands in its portfolio through the API. These include Kroger, Bakers, City Market, Dillons, Food 4 Less, Foos Co, Fred Meyer, Fry’s, Gerbes, HayC, King Soopers, Metro Market, QFC, and others.

From a business point of view, these brands all exist independently from one another to the consumer, presenting their own shopping experience, containing their own stock, and, in many cases, holding their own pricing strategies and premiums. For Kroger partners, however, a greater level of interconnectivity is necessary to function as a business, especially when you consider that a Food 4 Less could, in theory, be right next to a Kroger. As such, a pricing issue might result in a substantial business revenue impact.

The Kroger Partner API also surfaces a lot of customer context, allowing API users to either act as a customer or act on their behalf, delivering substantial customer service and commerce data ability to partners. This, in turn, boosts the potential business upside and creates more avenues of success for revenue partners.

Partner APIs Drive Interoperability

Partner APIs drive so much of the online experience despite their relative invisibility to the average end user. While these examples are powerful ones, for every example on this list, countless other high-profile partner solutions are driving the modern web towards greater interoperability, scalability, and extensibility. As the API space develops and expands, users should expect even more rich partner services to surface.