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🔍 What is Application Programming Interface? Let's explain with examples.

Application Programming Interface (API) is a set of definitions created so that a software can use functions defined in another software and transfer data between them. API; It can be used for web application, operating system, database, hardware or software library.

API can also be thought of as a user interface (UI) designed for software. User interfaces allow users to communicate with computer programs. API helps computer programs to communicate with each other.

For example, when you upload a post to Instagram, you will not be aware of 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.

Likewise, a computer program can be connected to another computer program by API. Let's say we integrate programs A and B with API. After the integration is established, program A can receive data from program B and display these data itself. Or it can ask program B to perform any action. Program A does not know how this data is processed or how the processing takes place. Just like in the user interface, it only transmits the required messages via the API and program B performs the desired operations in accordance with these messages.

The usage area of the API is quite wide. It is used as a contract that provides communication between client and server, especially in web-based applications. So much so that the client requests data in a specific format and in any case receives a response from the server in a specific format. This case is also called WebAPI as a special form of API.

Examples of WebAPI include interfaces offered by popular services such as YouTube API, Google Maps API, Twitter API, Facebook API. Thanks to these interfaces, developers can benefit from the data or functions offered by these services.

What are the advantages of the API?

- Thanks to the API, data exchange between software is facilitated and integration is provided.

- Thanks to the API, developers can develop new applications or features by taking advantage of existing services or platforms.

- Thanks to the API, the performance and security of the software increases.

- The API makes it easier to maintain and update software.

- Thanks to the API, the usability and accessibility of software increases.

How does the API work?

The working logic of the API can be summarized as follows:

- An application or service (client) requests data or action in a certain format from another application or service (server).

- The server evaluates the client's request and responds in a specific format if appropriate.

- The client uses or displays the response from the server in its own application.

In this process, communication between client and server usually takes place over the HTTP protocol. The HTTP protocol is a standard protocol used to access resources on the web. There are four basic methods in the HTTP protocol: GET, POST, PUT and DELETE.

These methods mean:

- GET: Used to retrieve or view a resource.

- POST: Used to create or send a resource.

- PUT: Used to update or change a resource.

- DELETE: Used to delete a resource.

In addition to these methods, additional methods such as PATCH, HEAD, OPTIONS can be used in some cases.

The format of data exchange between client and server is usually determined as JSON (JavaScript Object Notation) or XML (Extensible Markup Language). JSON and XML are text-based formats that structure data to make it readable and portable.

A data in JSON format looks like this:


   "name": "Ali",

   "surname": "Yilmaz",

   "age": 25,

   "occupation": "programmer"


The same data in XML format looks like this:







Thanks to these formats, the data between client and server becomes easily understandable and processable.

How is the API developed?

Various languages, platforms and tools can be used to develop APIs. For example, it is possible to develop RESTful APIs with languages such as Python, Java, C#, PHP. RESTful API is a popular type of API that uses the HTTP protocol to access resources on the web.

Various frameworks such as Flask, Django, Spring Boot, ASP.NET Core, Laravel can also be used to develop RESTful APIs. Frameworks streamline the API development process by providing developers with ready-made pieces of code and builds.

Various tools such as Postman, Swagger, Insomnia can also be used to develop APIs. These tools provide facilities for testing, documenting and sharing APIs.

How to learn API?

To learn API, you must first have basic programming knowledge. It is important to know at least one of the programming languages and understand the basic concepts on the web.

It is also possible to benefit from various resources to learn API. For example:

- Online courses: There are various API-related courses on platforms such as Udemy, Coursera, and Codecademy.

- Books: Books such as Web APIs for Dummies , RESTful Web APIs , Designing Web APIs can be useful on API.

- Articles: There are many API-related articles on sites such as Medium,, Hacker Noon.

- Videos: There are many videos about the API on sites such as YouTube, Vimeo, TED.

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