What Are the Different Types of APIs

In today’s digital age, sharing data and functionality between software applications is becoming increasingly important. There are many ways to connect these software and applications, and APIs (Application Programming Interfaces) support these integrations in the background. This makes it easier to communicate and exchange data between different software and applications. But not all APIs are created equal. That’s why developers use various types of APIs to suit the business needs of enterprises. In this blog, we’ll explore what these APIs are, the different types, and what to consider when choosing the right API type.

What is an API?

An API is an interface that allows a software application to communicate with other applications or systems. Basically, it provides access to certain functions or data sources of an application. For example, a weather app can pull weather data and provide weather-related information through an API, or a payment processing app can provide payment history information through an API.

What are the Different Types of APIs?

There are basically four API types: public, internal, partner and composite. In addition, three different API architectures determine how APIs work and how data is shared. We will examine all of these one by one.

Public APIs

Public APIs are also known as Open APIs or external APIs. This type of API acts as a bridge between external developers and the general public without any restrictions. In other words, Open APIs foster collaboration by connecting a business’s internal systems or services with external stakeholders. This open access model supports innovation and enables the creation of a broader ecosystem around the organization’s services or data.

Partner APIs

Partner APIs are shared externally, but only between those who have a business relationship with the API provider. Access to these APIs is limited to authorized customers with official licenses, so security measures are generally more robust than for public APIs. In this way, the business medium

Internal APIs

Internal APIs are only shared for internal use within organizations, so they are only accessible within the organization. Unlike public or partner APIs, they are completely closed to access by an external party. The purpose of an internal API is to enable data exchange and communication between internal systems. Therefore, they are designed in accordance with the security policies of organizations and use security mechanisms such as strong authentication and authorization to allow only authorized personnel to access them. Thus, they ensure data security by keeping the flow of data within the company under control.

Composite APIs

Composite APIs combine two or more APIs to create a set of interconnected operations. In other words, composite APIs allow developers to combine multiple APIs to combine calls or requests and receive a single unified response from different servers.

Such APIs can be used when data is needed from various applications or to initiate an automated chain of calls and responses without intervention. In this way, developers can manage data from different sources in one place and increase the functionality of their applications.

What are API Protocols and Architectures?

API protocols and architectures include the rules by which APIs work and how data is shared. There are basically three types of API protocols: SOAP, REST and RPC. Each API protocol has its own specific use cases and applications.


REST (Representational State Transfer) is one of the most widely used API architectures and is notable for its simplicity. RESTful APIs work based on the principles of stateless communication and resource-oriented architecture. These APIs interact with resources represented through URLs using standard HTTP methods. They usually exchange data in various formats such as JSON or XML, which facilitates communication between different systems. REST’s simple and easy-to-implement structure, as well as features such as caching and statelessness, make it a common choice.


SOAP (Simple Object Access Protocol) is a communication protocol that uses XML format in its messages and is based on strict rules. The main features of SOAP APIs are their robustness, security features and strict adherence to standards. They define API operations through features such as message validation, error handling and a predefined contract, the Web Services Description Language (WSDL). SOAP’s reliability and support capabilities for complex transactions make it particularly suitable for applications with high security and reliability requirements, such as financial services and healthcare.


RPC (Remote Procedure Call) is one of the simplest types of API and allows a program to perform an operation on a remote server, such as calling a local function. This protocol is used to run a procedure or function located on a remote server in a local program. RPC-based APIs often play an important role in scenarios that require low-level system interactions, but they are less widely used. Such APIs are particularly suitable for applications that require efficient and low-level communication, such as distributed systems and real-time applications.

Examples of APIs Used Today

APIs have become an indispensable part of many modern software platforms and even a must-have. Everyday computer users make use of a wide range of APIs, even without realizing it. Here are some current API use cases:

Social Media APIs

Social media platforms such as Twitter, Facebook, Instagram with many users use APIs to communicate between the platform and remote endpoints.

Authentication and Login APIs

Nowadays, websites, applications, etc. Many platforms rely on APIs to provide single sign-on.  For example, an application may offer login options through “Google or Facebook” for a user to log in to the application. This eliminates the need for users to create a new account for the apps and sites they want to access. However, this API effectively consolidates the authentication of multiple applications in the background.

Finance and Payment APIs

Remote users of banks need to connect to the bank’s back-end systems to perform remote deposits, withdrawals, transfers and electronic payment transactions. This connection is achieved through APIs. For example, a financial business like PayPal uses APIs to connect the user to their PayPal account.

Travel and Hotel Booking APIs

Users planning airline trips and buying tickets use the airline’s API, while users looking for accommodation and booking rooms use the hotel company’s API.

How to Choose the Right API Type for Your Business

Each API has its own distinct advantages and disadvantages. The key is to choose the right type of API integration that fits the unique needs of your business and benefit from the best API management.

When making your API selection, it is useful to know the following and proceed accordingly:

Public APIs: If you want the API to be publicly available, expand your system and reach a wider audience, you can use public APIs.

Partner APIs: If you want to share your API with trusted external partners or companies, you can choose Partner APIs. This type of API enables secure and controlled data exchange and creates a trusted communication environment between the collaborating parties.

Internal APIs: If you want seamless communication and data sharing across your business, you can choose Internal APIs.

Composito APIs: Consider this API type if you want to combine data from multiple APIs into a single interface and simplify complex processes.

REST: If you need scalability, simplicity and ease of implementation, you can use RESTful APIs.

SOAP: If you need intensive security measures, such as transactions in the financial and healthcare sectors, you can choose SOAP.

RPC: If you need efficient, low-level communication in distributed systems or real-time applications, RPC-based APIs may be a good choice. Such APIs enable efficient communication and provide a reliable solution for exchanging data between distributed systems.

Onur Ergür
Digital Marketing Manager

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