API integration

What is an API integration?

An API integration is a piece of software that lets two systems talk to each other. It retrieves data from one system and puts it into the other. That happens via the API of both systems.

API stands for application programming interface. That is a fixed entrance to a software package, with agreements about which data you can request and send. Many business packages have such an entrance. Exact Online, AFAS and SnelStart, for example, offer one.

How does an API integration work?

The integration follows fixed rules, such as: every new order goes to the accounts. Sometimes the integration asks at fixed times what is new. Sometimes one system reports by itself that something has changed. That is called a webhook.

An integration works one way, or both ways. And it has to know what to do if something does not fit, for example an order without a customer number. A good integration then gives a notification, so that an employee can resolve it.

Standard integration or custom integration?

Many packages have ready-made integrations, often in their own app store or marketplace. Does such a standard integration do what you need? Then it is enough. A custom integration is needed if there is no standard integration, or if your data needs to flow differently from how the standard integration handles it.

In between sits the integration platform: an online service in which you put integrations together yourself.

Would you like a custom integration built? Read how I approach integrations and automation.

What should you watch for with an API integration?

• Access. The integration needs permissions in both systems, for example with an API key. Do not give more permissions than necessary.
• Personal data. Does data about customers or employees pass through the integration? Then the GDPR applies. Does the integration run at another party, or can that party access the data? Then you sign a data processing agreement with that party.
• Errors. Agree who gets a notification if the integration cannot process something.
• Maintenance. Packages sometimes change their API. An integration therefore needs maintenance.

An integration is not needed for everything. If it concerns a few lines a week, retyping is sometimes fine. An integration suits work that comes back often and goes the same way every time. Read more in What is an API integration? Explanation for business owners and in what an API integration costs.

Frequently asked questions

Sources on the APIs: Exact Online REST API, AFAS: connecting external software with Profit (in Dutch) and SnelStart: requesting an API integration (in Dutch). Consulted on 7 October 2026.