APIs Explained Simply: What They Are and When You Actually Need One

When you have software built or want to connect two systems, sooner or later the word API comes up. Usually it gets thrown around as if you should already know what it means. This article explains, in plain language, what an API really is, how it works and – honestly – when you need one and when you don't.

What is an API, really?

API stands for Application Programming Interface. Put simply, an API is a clearly defined door through which two programs talk to each other, without a human sitting in between.

Here's a useful picture: imagine a restaurant. You're sitting at your table (your program) and you want something from the kitchen (another system). You don't walk into the kitchen and cook yourself – you tell the waiter what you'd like. The waiter is the API. He knows the rules, takes your order, passes it on and brings back the result. You don't need to know how the kitchen works internally. You only need to know what you're allowed to order and in what form.

How does it work technically?

In practice, a program sends a request to a specific internet address and gets a structured response back – often in the JSON format, which both machines and humans can read. Most modern interfaces are so-called REST APIs, which run over HTTP, the ordinary protocol of the web.

A typical API defines the following:

• Endpoints – the addresses you can call (for example, to retrieve a list of customers)
• Methods – whether you want to read, create, update or delete data
• Authentication – usually an API key or token, so that not just anyone can access it
• Data format – what the request and response need to look like

The beauty of it: whoever uses the API doesn't have to understand the inner workings of the other system. The interface is a contract. As long as both sides stick to it, the exchange works reliably.

When do you need an API?

An API is not an end in itself. You need one as soon as systems are meant to exchange data automatically. Typical situations include:

• You want to integrate third-party services: payment providers, shipping carriers, maps, AI models, accounting software – almost all of them offer APIs that let you bring their features into your own tool.
• Two of your own systems need to stay in sync: for example, your online shop and your inventory system, so stock levels are always correct automatically.
• You're building an app or a SaaS yourself: in that case the frontend (what the user sees) usually needs its own API to communicate with the backend (database and logic).
• You want others to work with your data: if partners or customers should be able to use your content programmatically, you provide them with an API.

When you DON'T need an API

Here we're deliberately honest, because APIs are often sold as the solution where there's no problem at all. In most cases you don't need your own API when:

• you want a simple website or one-pager that shows information and has a contact form
• your content is only ever meant to be read by people in a browser anyway
• an off-the-shelf tool already covers the task and no connection to the outside is needed
• a one-off, manual data transfer is enough – in which case a simple export is cheaper than an interface

An API costs development, maintenance and security effort. If nothing needs to be exchanged automatically, that's wasted money.

What to look out for in an API

When an API genuinely makes sense, a few things determine its quality:

• Documentation: an API is only as good as its description. Without clear docs, every integration turns into guesswork.
• Security: authentication, encryption and rate limiting are part of the standard, not optional extras.
• Stability: if the interface keeps changing, every connected system breaks. Versioning creates reliability.
• Error handling: a good API tells you clearly what went wrong, rather than just failing silently.

Our experience with this

We run seven of our own brands in production – including a product portal with more than 177,000 records, a marine SaaS and an industrial marketplace. These systems hang off numerous internal and external interfaces: payment processing, data imports, AI services, search indexes. From this day-to-day work, we know where an API delivers real leverage – and where it only adds complexity.

That very judgement is often more valuable than the interface itself. The right question is never just how we build an API, but first: do you really need one at this point? If yes, it pays to plan it properly. If no, you save yourself ongoing costs – and we'll tell you so.