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.
A successor to the WOEID project is Who's On First.