What Is the Difference Between Postcode APIs in the Netherlands and Belgium?
Discover the difference between postcode APIs in the Netherlands and Belgium. Learn why addresses in Belgium are harder to validate and how to solve it with smart APIs.
Dutch and Belgian postal codes look similar at first glance, but technically they are fundamentally different. That difference has major consequences for how you implement address validation in your webshop or application.
The Dutch Postal Code System
Dutch postal codes consist of 4 digits + 2 letters (e.g. 1234 AB). Every combination of postal code + house number is unique and refers to exactly one address in the Basisregistratie Adressen en Gebouwen (BAG).
This makes a Dutch postcode API straightforward to implement: send postal code + house number to the API and you get back one clear answer with street name, city, municipality, and GPS coordinates.
The Belgian Postal Code System
Belgian postal codes consist of 4 digits (e.g. 2000 = Antwerp). One postal code covers an entire municipality or even multiple sub-municipalities. One postal code can therefore contain dozens of streets, and house numbers are not centrally registered as they are in the Netherlands.
The consequence: in Belgium you cannot simply provide postal code + house number and get back one address.
Why a Postcode API in Belgium Is More Complex
In Belgium there is no nationally registered link between postal code + house number and a specific address. The alternatives are:
-
Autosuggest on street name: The user types their street name, and the API filters in real time based on postal code. With
1000(Brussels) and the inputLoui, suggestions like Louisalaan, Louis Schmidtlaan, and Louizaplein appear. -
Full address entry with validation: The user enters the full address and the API checks whether it exists.
Implications for Webshops and Applications
| Netherlands | Belgium | |
|---|---|---|
| Unique address on postal code + house number | Yes | No |
| Street name autofill possible | Yes, directly | Yes, via autosuggest |
| Central address registry | Yes (BAG) | No equivalent database |
| GPS coordinates available | Yes | Yes |
How ApiCheck Solves the Difference
ApiCheck supports both countries with one API key and two different endpoints:
- Netherlands (Verify API):
postcode+housenumber→ direct address result - Belgium (Search API):
query(street name) +postcode→ list of suggestions
Your WooCommerce, Magento 2, or Contact Form 7 plugin automatically detects whether a customer is entering a NL or BE address and switches between the two methods.
Conclusion
Dutch and Belgian address validation are fundamentally different. ApiCheck offers one integrated solution for both countries — including GPS coordinates and support for 15 other countries. One API key, one implementation.