A WOEID (Where On Earth IDentifier) is a unique 32-bit reference identifier, originally defined by GeoPlanet and now assigned by Yahoo!, that identifies any feature on Earth. [1] In 2009, Yahoo! released GeoPlanet's WOEID data to the public, [2] with the last release on 1 June 2012, after which Yahoo! decided to cease making the data downloadable until they "determine a better way to surface the data as a part of the service". [3]
WOEIDs are used by a number of other projects, including Flickr, [4] OpenStreetMap, [5] Twitter, [6] WOEID Search Engine (archive link) and Nations24.
From WOEID Search Engine: [7]
E.g. Berlin does not know about Germany, which itself doesn't know about Europe and so forth.[ clarification needed] GeoPlanet records, or places as they are called by Yahoo!, always (except one) have a reference to its parent place and therefore offer relations between places like the following: [8]
If you take e.g. our company's district you will get the following family tree: