Error codes

Ordnance Survey uses standard HTTP response codes to provide key information on the outcome of API requests. These codes serve as a straightforward means of communication, indicating the success or failure of each API request between your application and our APIs.

When a request is successful, you'll encounter codes within the 2xx range. If the information in the request is incorrect (for example, missing query parameters), you'll receive codes within the 4xx range, and 5xx codes indicate an error with the OS APIs.

The following table details the HTTP response codes and their meaning within the context of OS APIs:

Code	Official description	Explanation in context of the API
200	OK	Request has been successful.
304	Not Modified	In response to a conditional GET request this response indicates that the underlying data has not changed since the previous request, and cached results may be re-used.
400	Bad request	For example, missing query parameter or malformed syntax.
401	Unauthorized	The client has not provided authentication or has provided incorrect authentication.
403	Forbidden	The client has authenticated its access but does not have sufficient rights to complete the request.
404	Not found	The server has not found anything matching the Request-URI.
405	Method not allowed	The request used an unsupported HTTP method, for example, DELETE or PUT.
429	Too many requests	The number of requests per minute (rate-limit) has been exceeded.
500	Internal server error	A generic internal server error occurred.
503	Service unavailable	A temporary outage due to overloading or maintenance.