The Office for National Statistics (ONS) Address Index API provides public sector organisations with address lookup functions, via HTTP. It allows users to look-up addresses in England and Wales, and to select and retrieve the official address.
The API is currently only available within ONS, though there are plans to make the bulk match part of the system available via the new IDS (Integrated Data Service).
Work is also underway to create a new version of the system using Natural Lanugage Processing.
The Address Index API provides a number of end points to enable address look-up.
Each end point and its basic purpose are available from the Explore the API readme.
A Swagger 3 also known as openAPI 3.0.0 definition is also provided.
The Address Index Simple Tester allows users to use the various functions available via the API, providing an input request and receiving a response from the API.
A number of code samples are provided as a starting point for using the API