Digitalisering
26. juni 2025
What is an API?
API is an abbreviation of Application Programming Interface, and it is a set of rules that enables different systems to communicate and exchange data. In short: it is a kind of digital intermediary that ensures two programs can understand each other—without having to speak the same language.
Indhold
Hvordan fungerer API’er Hvordan bruger man dem Eksempler på API’er Find frem til API’er Best practice FAQHow do APIs work?
Imagine ordering food via an app. You choose a burger, tap “order”, and the magic happens. But it is not magic—it is an API.
The app forwards your order to the restaurant via an API. The restaurant responds via the same API with “order received” and later “your burger is on the way”. Without the API, the app and the restaurant would have to develop a unique integration—and that would be both cumbersome and expensive.
In practice, the API acts like a digital waiter, carrying messages back and forth quickly and efficiently.
How do you use them?
You use APIs every day—without even thinking about it.
When developing digital solutions, you typically use APIs to:
| Use case | Example |
|---|---|
| Retrieve data | For example, products from an ERP system to a webshop |
| Send data | An order from a customer |
| Connect systems | For example, a CRM system with an email tool |
| Extend functionality | For example, map display via Google Maps or data processing |
This happens via calls—a request is sent, and you receive a response back. Often in JSON format.
Examples of APIs and how they are used
Here are some classic (and widely used) APIs:
👉 Google Maps API – displays maps and routes directly in your app or website
👉 Facebook Graph API – provides access to posts, likes, and ads
👉 Stripe API – handles payments securely and easily
👉 NemID/MitID API – integrates login and secure identification
👉 Pakkelabels.dk API – automatic creation and printing of shipping labels.
If you have used an app that displays something from another platform, then you have (almost certainly) used an API.
How do you know whether there is an API?
Most larger systems and platforms today have an API. And fortunately, it is not secret knowledge.
Check the following:
- Find the documentation—often listed under “developers” or “API docs”
- Google “[system name] + API”—it works surprisingly well
- Ask support—they will know
- Use developer tools (or a curious developer) to do a bit of digging
If there is an API, you will most often get access via a key (API key) and some documentation.
Best practice when working with an API
Here are our key recommendations when working with APIs:
- Read the documentation—it is not a novel, but it will save you hassle
- Test your calls in Postman or similar. —quickly and efficiently
- Handle errors—APIs do not always respond nicely
- Ensure security—API keys must be treated like passwords
- Consider limitations—many APIs have rate limits
- Keep an eye on versions—APIs are updated and can change
APIs are not dangerous—but they require diligence. It is not plug-and-play, but it is close.
FAQ about APIs
Do I need to be a developer to use an API?
Does it cost money to use an API?
Is it safe to use an API?
Can I create an API myself?
What do I do if the API does not work?
