What are the types of APIs and their differences?

By Marie Singer

API – Application Programming Interface

APIs are rules and protocols to help two or more computing devices or applications communicate effectively. APIs are defined according to the organization’s business needs. APIs act as an interface to interact between apps and share data sets. Organizations make the best use of APIs in Custom Software Development for better operations and performance. Each API is assigned rules to send or receive data and protocols to be followed when using the APIs. There are various types of APIs available in the market that serve different purposes. Organizations use diverse technologies to implement APIs depending on the feasibility, context, and specific requirement.

Types of APIs

There are different types of APIs available on the internet. These APIs are categorized into four types depending on the predefined rules and protocols.

  1. Public APIs
  2. Open APIs
  3. Private APIs
  4. Partner APIs
  5. Composite APIs

  • Public APIs:

Public APIs are available to the developers to perform generic tasks such as accessing data, functionalities, or services while building web or mobile applications. Protocols used in these public APIs are generic and can be accessed according to the developers’ wishes and application needs. These APIs are available in the generic apis community, where the developers share a massive set of apis that serve versatile purposes. Different developers follow a different set of rules and protocols while developing an API. Public APIs are documented and published to assist developers in integrating the APIs into their applications. The document includes an introduction, endpoints, request parameters, response formats, error handling, code samples, SDKs, libraries, guidelines, and best practices. 

Public API Examples:

TwitterAPI is a publicly available API that allows developers to retrieve, post, search tweets and interact with other Twitter users. 

  • Open APIs

The term “open“ refers to the accessibility and transparency of the API. It is a standard used in defining a set of protocols for an API. OpenAPIs are those for which the developer follows OpenAPI Specification (OAS) while developing. The OpenAPI documentation defines the overall API structure, endpoints and operations, input and output data validations, possible errors and responses, security constraints involved, and authentication mechanism. These are generally available to all the audience without restrictions unless specified.

Open APIs are beneficial when the application requires multiple integrations among different systems, ecosystem expansion, collaboration, and partnership API development. 

OpenAPI Examples:

OpenWeatherMap API forecasts global location weather to help developers to fetch data such as temperature, humidity and wind speeds, and anticipated climate conditions.

  • Private APIs

An API used to do a specific task and accessed by a particular organization or a  group is called a private API, also known as an internal API. Unlike public or open apis, these are not accessible by the public other than specified group or firm, restricting the access within the firm’s network infrastructure. Private APIs provide exceptional benefits to organizations, like enhanced scalability and reusability following Service Oriented Architecture(SOA), complete control over the data, superior data security, and a streamlined workforce. API integration software checks with the protocols and authorizes the user before accessing, providing information security. Most large enterprises use Private APIs to manage their workforce and customer databases, where data security is prioritized.

Private APIs Example

An organization’s custom software development API, Customer Relationship Manager(CRM), manages all the customer KYC and their association with the organization.

  • Partner APIs

Enterprises that operate the majority of their operations with B2B use partner APIs to interact with their partners. Partner APIs provide customized access to data sets of every partner firm, allowing them to offer value-added services. Third-party applications also use Partner APIs to share existing features of the same sector services rather than developing a whole new API. This API is beneficial when the business integration needs are temporary, and you have to access a set of data from a partner for a dedicated period. Customized functionalities and restricted access make partner APIs the best solution for firms looking for short-term collaborations.

Partner API Example:

Travel platforms develop custom software with partner APIs to allow travel agencies to share their real-time availability and prices with the audience. 

  • Composite API

It is a special type of API that lets one single endpoint of an application interact with multiple endpoints of numerous APIs using a single composite API. Instead of making numerous one-to-one API calls, composite API is used to make one-to-many calls to gather responses as one and perform the specified action.

Composite API Example:

GraphQL API by Github is an example of composite api, which makes API calls to get data about repositories, pull requests, issues, etc., and combines data into one.

Differences between APIs

Depending upon the business need, developers and CIOs can opt for a specific type of API while developing custom software. Each of the mentioned APIs has its own importance in building custom apps. Key differences among the APIs are:

Public APIs:

  • The general audience and external developers can easily access it.
  • Third-party developers can reuse the generic APIs
  • Examples: Google Maps API and Twitter API.

Open API:

  • Follows standardized format while developed.
  • The primary focus is on technical documentation and specifications.
  • Examples: Any APIs using OpenAI Specification.

Private APIs:

  • Specific organizations or a group only can access it.
  • Improved security.
  • Examples: Internal CRM system API, and Library Management API of the educational institute.

Partner APIs:

  • Exposed to selected partners or trusted third parties.
  • Enables data sharing and collaboration among partner entities.
  • Examples: Financial institution API for authorized partners.

Composite APIs:

  • Multiple APIs responded aggregated into a single interface.
  • Unified access simplifies diverse system integrations.
  • Examples: Social Media Analytics API.

In conclusion, public APIs are for the general public audience, open API is for standard documentation, private APIs are for internal use, partner APIs are for partner firms, and composite APIs are to integrate multiple API responses.