Purple circles represent net additions, red circles represent net subtractions.
The bigger the circle, the larger the edit (circle radius is proportional to the log of the size of the edit in bytes).Why are only anonymous user edits displayed on the globe? Anonymous users are identified by their IP address, which can be converted to a geolocation. Registered humans and bots are identified by their usernames, which have no geolocation information attached.
Made by Sacha Saint-Leger
Source can be found here