GeoJSON is a format for describing geo-data using JSON.

GeoJSON demo

In 2015, the IETF (Internet Engineering Task Force) and a group of authors of the original specification joined together to form the GeoJSON Standardization Working Group. In 2016 they published RFC7946 “The GeoJSON Format”:

This is where you can interactively create/debug GeoJSON:

By the way, as of 2019, this is the format Apple recommends adding data to the map when using their MapKit/MapKit JS:

Moreover, Apple has created a GeoJSON-compatible IMDF (Indoor Mapping Data Format) for describing rooms:

Go library:

2020-05-06 Edit