What Is an API? A Guide to How APIs Work and How to Use Them

Written by Coursera • Updated on

This article defines API and offers a succinct exploration of what APIs do, how they work, and how readers can use them, including getting into back-end development.

[Featured Image]  A back-end developer in a gray sweatshirt uses their laptop to work on an API with nearby coworkers.

What is an API?

API stands for application programming interface. An API is a set of protocols and instructions written in programming languages such as C++ or JavaScript that determine how two software components will communicate with each other. APIs work behind the scenes to allow users to locate and retrieve the information they request.  

Think of APIs like contracts that determine how two software systems will interact. Consider a few examples of APIs in action and how a website owner or administrator might use APIs in the following situations:

  • The YouTube API allows you to add videos to your website or app, as well as manage your playlists and subscriptions. 

  • The Facebook API for conversions allows you to track page visits and conversions, as well as provide data for ad targeting and reporting.

  • The Google Maps API allows you to embed static and dynamic maps, as well as street view imagery, on your website. 

As an internet user, you’ve most likely experienced the convenience API technology enables when browsing a website or using a mobile app. Let’s apply the above examples to the user experience. Anytime you land on a site and watch a video, see an ad on Facebook related to a website you recently visited, or use the map on a business’s website to find its physical location, chances are an API has been at work to make this experience possible. 

Types of API

Now that you have an API definition, the next step is to become familiar with the different types of APIs.

  • Open APIs, also known as external or public APIs, are available for anyone to use and integrate with their sites or apps. 

  • Partner APIs are also considered external, but you can use them only if you have a business relationship with the companies providing them.  

  • Internal APIs, also called private APIs, are used by people within a company and help to transfer data between teams or connect different systems and apps. Third parties do not access internal APIs like they do with open or partner APIs. 

  • Composite APIs combine multiple APIs from different servers or data sources to create a unified connection to a single system. 

API architectural styles

  • SOAP stands for simple object access protocol. This protocol determines how to transmit data across networks, how messages should be sent, and what the messages should include. 

  • REST stands for representational state transfer. It’s a set of guidelines for scalable APIs that are easy to use when transferring data securely. 

  • RPC stands for remote procedural call. RPC APIs execute code on remote networks.   

To find out more about different types of APIs, watch this video from the Meta Back-End Developer Professional Certificate

Explore the definition of API and different API types

How do APIs work?

Most web APIs function as follows: 

1. The user performs a task on a website or app, such as clicking a video to watch it. 

2. This action tells the site or app to initiate an API call, which means to submit a request to the API for information from the external server or program. 

3. The API then retrieves the requested data and delivers it back to the app, so the user has the expected experience. 

Cloud APIs enable cloud applications to communicate with one another. As organizations deploy more programs and services on the cloud, cloud APIs will become more vital to how we use the internet. 

Benefits of using APIs 

The use of APIs is increasing. They benefit businesses, users, and developers in the following ways: 

  • Businesses can access and share content from other software systems.

  • A company’s employees can work faster on tasks and collaborate more easily with coworkers.

  • Internet searchers can find information and interact with sites easily. 

  • External users of apps and digital products can enjoy seamless customer experiences.

  • Developers can often build upon or modify existing APIs, rather than having to create entirely new ones, to deliver value to customers more efficiently. 

  • APIs provide security, so data from one device or server is never fully exposed to another. 

Get started in API development

A logical place to start in API development is to enroll in an introductory course or certificate program, such as the Meta Back-End Developer Professional Certificate. By enrolling in this program or similar ones like IBM's Full Stack Software Developer Professional Certificate, you can build essential skills in programming languages, front-end development, back-end development, and API coordination, as well as explore the different uses for APIs. 

You’ll also want to familiarize yourself with different API tools such as Postman, Akana, and Swagger

Once you are comfortable with skills and tools, your next steps would include:

  • Designing and developing APIs

  • Testing each API’s function

  • Publishing your APIs

  • Creating thorough documentation to encourage their adoption 

  • Monitoring their performance, in terms of engagement 


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