Any time you upload data to your account as a tileset, Mapbox gives it a map ID.
Map IDs will always start with your Mapbox username followed by your tileset's unique handle:
username.handle. Note that styles made in the Mapbox Studio style editor and datasets uploaded to Mapbox Studio or created through the Mapbox Studio dataset editor do not have map IDs. Rather, they are identified with style URLs and dataset IDs.
Map IDs are also used to identify projects created with Mapbox Editor and styles created with Mapbox Studio Classic. Both Mapbox Editor and Mapbox Studio Classic are legacy products and are no longer in active development. To learn more about our newer mapping tools, use Mapbox Studio.