Types of APIs

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API stands for Application Programming Interface – it’s a fancy way of saying it’s a pipeline for data to flow between two different applications. As you build a business, product or internal application there becomes a need to eventually integrate two or more applications. When we integrate two or more applications we begin using an API.

When we build an API, we need to keep in mind the purpose for it and that really ends up defining the type of API we have built.

There are a few major API types:

Open API (public API)
Partner API
Internal API (private API)
or Composite API

Open API

An Open API or public API is a service that has been made publicly available on the internet to allow developers to programmatically access a service.

Often these services are published to encourage third-party developers to build some sort of connection which then encourages greater use of the service and eventually more billing.

The priority of an open api is for it to be easily consumed and accessed by as many different clients as possible. A well designed open api should use standard data formats and open protocols. REST API and SOAP APIs are very commonly used.

Open APIs often very restrictive security and a lot of different use case restrictions – usually because they are free. If you need less restrictions or want to build a business around the API, you often have to join the Partner API.

Major social media networks like Facebook and Twitter have Open APIs.

Partner API

Partner APIs are pretty common – most large technology companies have them available. In a lot of ways, they are similar to the public or open APIs but they build ontop of them and often have a lot less restrictions.

A Partner API is exposed by the business to strategic business partners, there’s no public availability. A special and specific entitlement is needed to access them.

Usually software as a service providers provide them to integrators. Integrators have their developers access a special developer portal that allows them self-service and create keys to access specific client’s systems.

Shopify, Salesforce, Microsoft and NetSuite all have their own particular twists on them but they’re very similar. See the blog article Understanding the Different Salesforce APIs for more details about Salesforce’s.

Internal API (Private API)

Internal APIs or also known as Private APIs are hidden from external users and only exposed to internal systems. Internal APIs shouldn’t be meant for usage outside of the company. Usually an Internal API is used for efficient communication or reuse between services.

Composite API

Composite APIs tend to combine data from many different systems into one API endpoint that can be called. This allows a lot more efficient usage by integrators.