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What is an API?

Learn what an API is.
API stands for application programming interface. An API is a software intermediary that allows two applications to talk to each other. In other words, an API is a messenger that delivers your request to the provider that you’re requesting it from, and then delivers the response back to you. APIs connect applications and services on the web. This technology powers many of our day-to-day actions online from ordering goods, comparing prices, or even just checking the weather forecast. Let’s look at an example of how an API might be used when ordering goods, in this case pizza. If you were to order a pizza directly from a local establishment using their website, you can find a menu and input various details.
This might be the size pizza you want and your favourite combination of toppings. The restaurant’s app will check if they have ingredients in stock, calculate the total cost of the pizza, and return this information to you for you to confirm your order. But what happens if you want to find the best price for your favourite pizza from a selection of nearby pizzerias? Searching through each website individually, noting down the prices and comparing them all at the end would be a tedious process. Instead of checking each one individually, you could create an app to aggregate and compare prices for you. In order to do this, your app interacts with each pizzeria using an API.
The API acts like a messenger, taking your request and returning a response. Your app would ask each of the restaurants for information in this case, the price of a specific pizza by sending a message to their API and return result from the restaurant’s application. While you might not find your local pizza shop has an API yet, it’s likely that larger chains are already providing this functionality. APIs are increasingly becoming a must-have for businesses across a variety of industries. Besides allowing consumers to connect to their data like we saw when ordering from the pizzeria APIs allow organisations to integrate existing products with each other and with those of other vendors.
Your pizzeria for example, are likely using an API to connect to an external payment processing app to collect your payment. And there are many other ways that the pizzeria is likely leveraging APIs across its business. Using APIs to ensure their products and services can be accessed, aggregated, and integrated around the web.

In our increasingly connected world, how does data get from one place to another? Many of the tasks you perform online on a daily basis rely on sending and receiving information between different sites or services. These requests and responses are all possible thanks to application programming interfaces or APIs.

Watch the video to find out how APIs work.

APIs have been a longstanding concept in applications development. Originally, APIs were used to connect components running on the same machine. With the rise of computer networks and connected devices, more and more APIs have become available.

From government bodies to private corporations, these ‘vendors’ are increasingly providing outward-facing APIs that can be accessed over the internet. These APIs allow you to write code that interacts with a vendor’s system, or retrieve information and incorporate the response in your own applications. This process is known as API integration.

Some vendors provide ‘open’ access to their APIs, allowing anyone to connect and request information. Others require special permissions, or a fee, to gain access.

See also

Before moving on, let’s look at an article and a few videos to learn some more about APIs.

The following article is written by MuleSoft. This company was formed in 2006 and is a leading integration/API platform, based in California in the USA.

Now have a look at the following videos created by ProgrammableWeb, a news source owned by MuleSoft that covers all things API:

Now that we have covered common architectural patterns as well as APIs, it is time to check your knowledge.


  1. MuleSoft LLC. API development best practices [Article] 2020. Available from:
  2. APIs 101: What Exactly is an API? Part 1 [Video]. ProgrammableWeb; 2017 Jul 7. Available from:
  3. APIs 101: What Exactly is an API? Part 2 [Video]. ProgrammableWeb; 2017 Jul 7. Available from:
  4. APIs 101: How Does API Flexibility Help Me? Part 3 [Video]. ProgrammableWeb; 2017 Jul 7. Available from:
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