What is an Application Programming Interface (API)?

You may get confused about the term API usually used in tech language as they play an important role in the world of technology. So, what exactly API is? It stands for Application programming interface. Sounds complex? Let’s simplify it for you. Imagine you’re at a restaurant, you interact with the waiter to place your order, whereas you know that the food is prepared by the chef. Now in this example, think of the waiter as the API connecting the communication between you (the user) and the kitchen (the system)

Similarly, the API serves as a mediator in the digital world enabling different software systems to interact and communicate with each other. Similar to a menu at a restaurant, it specifies the techniques and data formats developers may use to trade and request information.

Types of APIs

Types of APIs

1. Web APIs

APIs accessed over the internet using the HTTP protocols are called web APIs. With these APIs, applications can interact with each other via standard web technologies. Services can also communicate and share data smoothly.

2. Library-Based APIs

Library-based APIs are also known as class libraries or framework APIs, developers can use the functions and procedures provided by it to simplify the complicated tasks within their code. 

3. Operating System APIs

With operating system APIs, applications can access the underlying resources and functionalities of any operating system. Programmers can use these APIs to write applications that communicate with file systems, hardware, and other system resources.

4. Hardware APIs

With APIs, software programs can interact with hardware devices like printers, cameras, sensors, and more. Developers may also integrate the capabilities of such devices into their apps by utilizing hardware APIs.

Why Are APIs Important?

Wondering why should you care about APIs? Well here’s the reason:

  1. API is super efficient as it streamlines the development process with pre-built functionalities which in turn saves the time and efforts of the developers.
  2. APIs empower different software systems to work together smoothly, promoting compatibility and collaboration.
  3. APIs promote creativity and the development of new services and apps by making features available to outside developers.

How Does An API Work?

Client-Server Communication

  • APIs work on client-server architecture, any type of application could be a client such as a web app, mobile app, or any software system. It starts communication by sending a request to the server. This request tells the action that needs to be performed or the data to be restored.
  • Most of the communication takes place over hypertext transfer protocol (HTTP). This request contains various parameters, headers, and sometimes authentication credentials, depending on the requirements of the API.
  • The server processes the requests according to endpoints and parameters including databases, executing business logic, or obtaining data from other sources.
  • The server processes the request generates an HTTP response containing the requested data or confirmation of the action performed and sends back the request to the client.
  • APIs use data exchange formats to structure the data being sent between client and server. This format may include JSON ( Javascript Object Notation) or XML ( extensible markup language). This format ensures that the exchanged information is understandable from both parties.
  • Status codes are also included in the HTTP responses to indicate the output of the request. These status codes may include 200 (OK), 400 (Bad Request), 401 (Unauthorized), 404 (Not Found), and 500 (Internal Server Error), among others. These codes help clients to understand if their request is successful or not and how to proceed accordingly. Each request from the client contains all the information necessary for the server to fulfill it. This simplifies the architecture and scalability of the system.


We can conclude that APIs work as the backbone of modern software development. It supports uninterrupted communication and integration between various systems. So, tech startups need to understand the APIs as it can help them to develop innovative products and services in today’s world.