The Postcode API uses the REST and JSON standards for communication.

Reference implementation

We provide a reference client implementation for PHP. This client implements authentication, error handling and caching.


Our APIs use the Cache-Control HTTP header to indicate how long the result of a call may be cached. We recommend implementing caching of retrieved results based on this header to improve the speed and efficiency of your application. Reducing the number of calls to our service may also keep your subscription costs down.

Forward compatibility

We will take care never to break existing fields or behavior without warning. Please note that we reserve the right to add new fields to responses in the future, so your client should ignore future unknown fields at any depth in the response.


HTTP Basic authentication is used, with the values of your applications Key and Secret used as username and password, respectively. You can obtain a Key and Secret by registering an application account.


Parameter values are added to the method URL according to the documented method URL template, and each parameter must be URL-encoded according to RFC 3986.

Please note that spaces must encoded as '%20' (not as '+'). Incorrect encoding of parameters can lead to incorrect API results.


Parameters (URL-encoded):

Rate limits

The number of requests per second your account can perform is limited. You can find the limits in the FAQ section.