What is an Application Programming Interface (And How Do They Work)?


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Tuesday, May 5, 2020

APIs are an integral part of any developer's toolkit. But what are they and why should you use them?

Article 7 Minutes
What is an Application Programming Interface (And How Do They Work)?

No business today can hope to be successful without fast access to data and the ability to display this in an easy-to-understand way. But with so many disparate applications, databases and servers to manage, ensuring information is gathered and used effectively can be a tricky prospect.

Fortunately, there are solutions available to developers to help make life easier - APIs. No matter what type of program you're looking to create, these will be an invaluable asset in ensuring your tools have all the functionality users expect.

What is an API?

API stands for application programming interface, and they're the backbone of today's constantly-connected online environment. Whether on web browsers or mobile apps, APIs provide the connections between users and data that are essential in giving people and programs the information they need quickly and easily.


On a basic level, APIs allow applications to talk to each other and exchange information, thereby making life easier for both users and developers. For example, one of the most common examples of APIs in action is the use of comparison websites for insurance or flights.

If you want to book a trip between two cities, you could go to each airline's website individually, fill in your details and see what flights are available. But this is tedious and time-consuming, so it's far quicker instead to use a comparison service that will do the legwork for you. When you enter your details into one of these services, it’s an API that goes to each airline's database and fetches the results for you.

There are a huge number of APIs in use on the web today. Some of the other more common ones include the Google Maps API, which allows developers to embed a range of geographical features into their sites, while Twitter and Facebook use APIs to offer easier access to their services.

How do APIs work?

APIs consist of a series of functions and processes that enable an end-user application to access the features or information held by another application and turn this into useful insight.

One way to think of an API is like the waiter at a restaurant. The customer is the end-user and the menu is the public-facing application they interact with. Meanwhile, the kitchen is the back-end database holding the details they want. The waiter (the API) takes the order from the customer, along with any specific instructions they have, and delivers it to the kitchen, which prepares the food (or retrieves results from the database). The waiter then delivers the final dish back to the customers.

This means applications that are otherwise completely separate - which may be developed by a different company using different technologies that have no way to communicate directly - can easily work together to provide relevant information quickly. By following a clear set of rules, APIs can help developers gain access to powerful functionality from elsewhere on the internet.

The key types of API

There are several key types of API that developers need to be aware of. These tools are split into categories based on both ownership and level of access offered, as well as the communication protocols they use.

Web APIs

For ownership of web APIs, there are four main groups. These are:

  1. Open APIs: also referred to as public APIs, these are publicly available with no restrictions on who can use them
  2. Partner APIs: these require specific rights or licenses in order to access, and are usually associated with paid services
  3. Internal APIs: also known as private APIs, this covers APIs that are developed by companies to use within their internal systems and aren’t meant for use outside the organization. They’re usually designed to boost productivity and enhance products and services by sharing data and applications between teams
  4. Composite APIs: these tools combine different service and data APIs to run a sequence of tasks that are run as the result of an execution, and aim to speed up API processes

Web service APIs

There are also web service APIs, which are small applications that use URLs or web addresses to provide services to desktop, mobile, web applications and others. These come in a few common forms, such as:

  • SOAP: standing for Simple Object Access Protocol, this uses XML as a format to transfer data. Its main function is to define the structure of the messages and methods of communication. It’s especially useful for secure, highly-structured interactions, such as bank transactions
  • XML-RPC: this also uses XML to transmit data, but is a much older and simpler tool than SOAP and requires much less bandwidth
  • JSON-RPC: this is similar to XML-RPC, except that it uses the JSON format for data transmission rather than XML
  • REST: standing for Representational State Transfer, this isn’t a protocol like the other web services, but a set of architectural principles. Unlike SOAP, which has very strict rules and security processes that must be followed, REST gives developers more freedom. It’s also data-led, rather than function-led, and doesn’t require as much bandwidth as SOAP

The benefits to developers

Many APIs may seem simple to end-users - indeed, if they're implemented correctly, the processes are invisible. But in fact, they often have to pull together a complex series of rules, statements, and conditions in order to deliver results.

This makes them invaluable for developers, as any project would quickly spiral out of control if they had to build solutions manually to achieve the same results as those offered by APIs. But by integrating APIs into their applications, all they have to think about is the end result.

This makes them an invaluable part of any developer's toolkit, whether you’re creating applications for the web or mobile operating systems. For instance, if you're looking to develop an iPhone app, APIs give you access to functionality that lets you do much more than would otherwise be practical.

If you want your app to capture images from a user's camera, for example, without an API to connect your app to the phone's native camera app, you'd have to create your own camera interface from scratch, writing software that could interpret the information received from the hardware. This would be an impossible job for all but the largest development teams, but, thanks to APIs, it's not necessary. Instead, all developers have to do is use the Apple or Android camera API to embed the existing work into their app.

This applies to almost any platform and functionality. So, if you want to take advantage of an Android device's built-in fingerprint sensor to improve your user authentication, you can do that. Even relatively simple tasks like creating a dialog box in Windows can be achieved through the use of APIs, saving time and effort.

Learn more: 5 Pros (and 3 Cons) of API-Driven Architecture

Why APIs are important for businesses

APIs don't just make development work easier. They offer businesses access to a vast array of resources and functionality that would otherwise be out of reach, enabling them to add value to their applications and ultimately improve their profitability. Innovative use of APIs helps firms stand out from the crowd and gives consumers a compelling reason to choose them.

For instance, one of the most widely used APIs, is Google Maps, and there are a huge number of potential uses for this tool. Retailers can add an integrated Google Maps functionality to their website or app to help users find their nearest store, while real estate agents can use it to show prospective buyers exactly where their listings are and what the surrounding area is like.

Meanwhile, flight tracking services use the same API combined with radar data to create a real-time map of where aircraft are, while other tools connect with census information to create historical maps, presenting raw data in a clear, easy-to-use format.

As the amount of data available to businesses continues to grow, the use of APIs to connect with vast repositories of information and real-time analytics and processing tools will be essential in helping businesses harness this data and convert it into a useful format that makes life easier for users.

With innovations such as IoT sensors greatly expanding the range of raw data available, those firms that can use APIs to integrate this information innovatively into their apps can transform their applications to offer new services to both employees and customers.

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