Free tool

Free Dutch Postcode API

Look up the city and street for a Dutch postcode and house number. Free to use, no API key, no sign-up. Built and hosted on our own infrastructure.

Free forever No API key required No rate limit (for now)

Endpoint GET https://postcode.api.daltcore.com/v1/addresses

Try it in your browser

This is an early, unrestricted release. A rate limit may be introduced later as usage grows.

Example request

GET https://postcode.api.daltcore.com/v1/addresses
    ?postcode=8261AA&houseNumber=1

Example response

{
  "street": "Klokkensteeg",
  "city": "Kampen",
  "municipality": "Kampen",
  "district": "Kampen",
  "neighbourhood": "Binnenstad Kampen",
  "lon": 5.918772239519917,
  "lat": 52.55676280656684,
  "status": "Verblijfsobject in gebruik",
  "active": true
}

Reference

Parameters and response

Two query parameters, one JSON response. That is the entire API.

Query parameters

Parameter	Type	Description
`postcode`	string	Dutch postcode, 4 digits + 2 letters, no space (e.g. 1234AB).
`houseNumber`	integer	House number, digits only.

Response fields

Field	Description
`street`	Street name.
`city`	City or place name.
`municipality`	Municipality (gemeente).
`district`	District (wijk), per the CBS Wijk- en Buurtkaart.
`neighbourhood`	Neighbourhood (buurt), per the CBS Wijk- en Buurtkaart.
`lon`	Longitude (WGS84).
`lat`	Latitude (WGS84).
`status`	Official BAG registration status of the address.
`active`	Whether the address is currently active.

Errors

Status	Error	Meaning
`400`	`invalid_postcode`	Postcode is not a valid Dutch postcode (4 digits + 2 letters).
`404`	`not_found`	Postcode is valid, but no address exists for it and this house number.

Paid extension

Energielabel API

An extension to the DALTCORE Postcode API: look up the official energy label for a Dutch address, right alongside the existing postcode validation and address data.

Paid tier Requires API key 1,000 requests/month included

Endpoint GET https://postcode.api.daltcore.com/v1/energylabel

Example request

GET https://postcode.api.daltcore.com/v1/energylabel
    ?postcode=8261VS&houseNumber=7
X-API-Key: <your-key>

Example response

{
  "energyClass": "D",
  "energyIndex": null,
  "validUntil": "2030-06-26T00:00:00.000Z",
  "registrationDate": "2020-06-26T00:00:00.000Z",
  "surveyDate": "2020-06-26T00:00:00.000Z",
  "buildYear": 1930,
  "buildingClass": "W",
  "buildingType": "Rijwoning tussen",
  "buildingSubtype": null
}

Include with an address lookup

GET https://postcode.api.daltcore.com/v1/addresses
    ?postcode=8261VS&houseNumber=7&includeEnergyLabel=true
X-API-Key: <your-key>

Example response

{
  "street": "Parallelstraat",
  "city": "Kampen",
  "municipality": "Kampen",
  "district": "Kampen",
  "neighbourhood": "Binnenstad Kampen",
  "lon": 5.911557976475438,
  "lat": 52.55894342905999,
  "status": "Verblijfsobject in gebruik",
  "active": true,
  "energyLabel": {
    "energyClass": "D",
    "energyIndex": null,
    "validUntil": "2030-06-26T00:00:00.000Z",
    "registrationDate": "2020-06-26T00:00:00.000Z",
    "surveyDate": "2020-06-26T00:00:00.000Z",
    "buildYear": 1930,
    "buildingClass": "W",
    "buildingType": "Rijwoning tussen",
    "buildingSubtype": null
  }
}

No separate integration needed: if you already use the Postcode API, just request the energy label alongside the same address lookup. If no label is known for the address, energyLabel is null and the rest of the address data is still returned.

Reference

Parameters and response

Query parameters

Parameter	Type	Description
`postcode`	string	Dutch postcode, 4 digits + 2 letters, no space (e.g. 1234AB).
`houseNumber`	integer	House number, digits only.
`houseLetter`	string	House letter, if the address has one.
`houseNumberAddition`	string	House number addition, if the address has one.

Response fields

Field	Description
`energyClass`	Energy label class (A+++++ to G).
`energyIndex`	Underlying energy index value, when available.
`validUntil`	Date until which the label is valid.
`registrationDate`	Date the label was registered.
`surveyDate`	Date of the energy survey.
`buildYear`	Construction year of the building.
`buildingClass`	Building class code.
`buildingType`	Building type description.
`buildingSubtype`	Building subtype, when registered.

Access

This extension is a paid tier, gated behind a personal API key. Every customer gets their own key: contact DALTCORE to request one. Send it as a header on every request.

X-API-Key: <your-key>

Without a valid key you get 401 invalid_api_key.

Errors

Status	Error	Meaning
`401`	`invalid_api_key`	API key is missing, invalid or revoked.
`404`	`not_found`	Address exists, but no energy label is registered for it.
`429`	`rate_limited`	Monthly quota exceeded.

Every key has a monthly quota (1,000 requests by default, higher on request). The quota resets automatically at the start of each calendar month.

Data source

Built on official Dutch government data.

Addresses come from Kadaster BAG, area boundaries from the CBS Wijk- en Buurtkaart. Both are official open government datasets, kept in sync automatically.

9.6M Addresses covered

Every registered address in the Netherlands (Kadaster BAG).

Monthly BAG refresh

Address data refreshes automatically every month.

Yearly Wijk/buurt refresh

District and neighbourhood boundaries follow CBS's own yearly publication cycle.

Need more?

Questions, feedback or a use case that needs more?

Get in touch. We are curious what you build with it.

Contact DALTCORE

Email: info@daltcore.com
Phone: 038 202 28 59
Location: Kampen, the Netherlands

All systems operational

Infrastructure monitored 24/7.