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What Is an API? How Does an API Work?

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Software applications compete with each other to serve users around the world today. This competition has enabled applications to increase their performance and service quality with innovative approaches to software development processes. Microservice architecture, which we have often heard of lately, is an example of this. In this architecture, we separate a monolithic application into related software components to increase performance and efficiency. These software components exchange data with each other synchronously with the use of API. So have you ever wondered what is an API?

API is actually a pretty general concept that has more than one type. In this article, we will first find an answer to the question of what is an API. Then we will touch on API types, their working principles, and their advantages.

What Is an API?

what is an api

The term API is a computing interface that enables data communication and sharing between different applications. So, it is widely used to allow multiple software to work together as a whole, making the whole experience seamless. As a result, APIs enable businesses to find innovative solutions to streamline their business operations.

For example, when you upload a post to Instagram, you are not aware of the changes in the background software and you do not need to add anything to the software. What you do from Instagram’s user interface automatically transmits what needs to be done to the software behind it, and the process is completed.

What Are the API Types?

APIs are classified according to their usage patterns and architectures.

Types of APIs According to Usage Purposes

Internal API: Certain people use internal APIs exclusively, keeping them hidden from external users. It is mostly used for reuse and production.

Open API: APIs are open to developers and everyone else. Also known as a public API. It divides into two categories: paid and free.

Partner API: Companies that conduct business with a certain business partnership use Partner APIs to enable the coordination of systems in their joint operations. They are not open to everyone. For example, the e-commerce site communicates with the cargo company using the Partner API.

Composite API: Composite APIs are APIs that combine multiple data or service APIs, allowing developers to access several endpoints in a single call.

API Types According to Architectural Structure

REST API: REST API, short for Representational State Transfer, which stands for Representational State Transfer, is an API service that works using the HTTP protocol.

It uses certain functions from HTTP requests such as GET, POST, PUT, and DELETE. REST uses JavaScript Object Notation (JSON), XML, CSV, and more as the data format.

REST is a form of the architectural model often used to build modern web-based applications. It is very useful, easy to maintain, easy to integrate, and has a lightweight structure, making it one of the most preferred API types.

SOAP: SOAP, which stands for Simple Object Access Protocol, is an API architecture that provides data transfer with a tighter security structure.

In this architecture, communication is provided using XML format. It is more difficult to configure than the REST API. However, it has a strong security structure.

What Is the Working Principle of an API?

Many APIs are located between an application and a web server. When a user wants to perform an action from this application, the application sends the required action to the web server via API. Thus, the desired operation through the application is effectively performed with the internet server and the results are returned to the application screen.

In short, the API is a communication tool between the application and the web server. Of course, the working principle of the API is not limited to applications and internet servers. All machines and systems that need to communicate with each other can use the API.

What Are the Advantages of Using the API?

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APIs make it simple to manage existing tools or create new ones. Some of the advantages of APIs are:

  • Creates API firewall. The API sends only a single request to the server, transmitting data securely instead of sharing all the data with the common server.
  • API management provides developers with usage metrics, geographic usage statistics, and more data-specific information. This information is valuable for organizations to make data-driven decisions for better digital transformation outcomes
  • The API simplifies program development by enabling the resolution and reuse of complex software processes. This eliminates the need to re-develop the application when utilizing the API, allowing developers to allocate their time to working on new tools and features.

Some Examples of Useful APIs:


To sum up, API is a connection interface that a program uses to access data, server software, or other programs. It contains a set of rules that determine how two machines talk. Many applications today are used to obtain or provide data.

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Q: What Is the Importance of API (Application Programming Interface) Documentation?

A: The API documentation is a resource with sample code to provide users with the correct use and integration of an API. It is of vital importance to users. The good API documentation provides developers with detailed information on how to use the API, what parameters and requests to send, and expected response formats. This documentation eliminates the compatibility problem for users in the process of using the API. Moreover, it helps users quickly understand the API and integrate it seamlessly.

Q: How Many Categories of REST APIs Does APILayer Offer?

A: APILayer offers its users multiple APIs in 18 unique categories. Categories such as scraping, news, data, finance, images, and geolocation are categories that can be suitable for almost any project.

Q: What are the Differences between Web APIs and REST APIs?

Although modern Web APIs and REST APIs have similar architectural structures, they have some differences. Some of these differences are as follows:

  • Client and server coordination: A REST API has a loosely coupled architecture that allows developers to develop independently on the client and server sides. A Web API, by contrast, more precisely coordinates changes between client and server.
  • Interface: A REST API is architecturally apt to use industry-standard interfaces. A Web API uses custom interfaces depending on the API provider.

Q: Is REST API’s Response Format Variety More Than SOAP (Simple Object Access Protocol) Services?

A: Yes, it is. REST APIs have a richer variety of response formats than SOAP services. The response format of SOAP services is XML only. REST supports return formats such as plain text, HTML, XML, and CSV, especially the JSON (JavaScript Object Notation) format, which developers highly use this format to exchange data.

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I am a software developer who loves coding, learning new technologies, improving myself and researching.
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