What Is An API & How Do They Work?

We all hear that APIs are vitally important software components, and they’re often publicised by software providers as an asset which is available for users of their software. We use them all the time, whether they’re made by others or by ourselves. But one of the most common questions posed to us when we mention them is “what is an API and how do they work?”

Defining An API

The acronym API stands for Application Programming Interface. It’s defined as a software intermediary which allows multiple applications to talk to each other.

We’ve briefly mentioned APIs in our previous blog post about Bullhorn integration (which you can read by clicking here) but this post will go into more detail about why they are so important.

How APIs Work

What Is An API? Flow Diagram Visualisation

As you can see from the first diagram, the API sits squarely in between the two software systems. It functions like a messenger, delivering requests for data from one system to the other and then returning the retrieved data back in response.

Each of the systems to be linked will have an API End Point built into them, which you can think of like a plug socket, with the API attached to “virtual cables” which plug into the End Points.

What Is An API? System Linking Illustration

The End Points allow data to enter and exit their systems at either end, acting as gatekeepers. The specifics of what data is permitted to be transferred is built into the system by the software developers.


Fundamentally, APIs create connectivity between software systems, but at the same time they’re independent of the infrastructure of each of the systems they are communicating with. This decoupling (at the API End Point) provides a huge advantage, in that it allows individual systems to be altered without affecting anyone or anything else, as long as the information passed to the End Point stays the same.

Why Developers Love APIs

APIs are fast, in so many ways. They can dramatically simplify things for developers and therefore speed up the entire software development process, especially as they use standards that are known by all developers (HTTP, REST etc). Code doesn’t need to always be written from scratch when repetitive and complex processes are taken care of by APIs, and this also frees the developer team to think about the more impactful aspects of what they’re building for the user.

They’re also very secure when built to the accepted industry standards, using encryption, authentication, white/blacklisting and more. You can also monitor anonymised usage and activity if required.

How This Benefits Your Business

  • Connection – APIs can provide a consistent, automated way for partner networks to access and utilise your data (but only what you choose to share with them)
  • Brand/Product Awareness – Usage by third-parties can build brand awareness and increase audience size.
  • Efficiency – Automation and reusability can decrease operating costs and improve efficiency. They are also incredibly cost effective as they can scale proportionally with usage.
  • Product Possibilities – As well as using APIs to create and operate your products, they are also able to be turned into a product in their own right.
  • Compliance – If data needs to be shared with others, an API enables you to specifically control access to the data you provide. This ensures compliance with data sharing regulations such as GDPR by adhering to the Principle of Least Privilege.


APIs have transformed how developers work, how businesses and their customers interact, how data is protected when accessed and much more. They are flexible, efficient, and very secure when configured and built by experienced professionals.

We integrate existing APIs for many of our clients to link custom and pre-existing software solutions, and we also regularly build bespoke APIs from scratch. If you would like to know more about how to use APIs to deliver a better customer experience, develop products faster or link existing systems together, let’s talk. Click to contact us now for a free consultation chat.