Currently to find the map projections used in ArcGIS Online is really unclear. For a feature layer it is of less importance as they can be transformed, however tile layers can only be displayed on basemap in the correct projection. Also changing a basemap changes the projection. Neither the layer or the basemap show clearly what projection they are in. It would be really beneficial to simply display this in:
- the item details page
- on a basemap in the list of basemaps so you know what you are going to get
- In the corner of a Map in MapViewer so you know what projection you are looking at
Ideally this would be in the EPSG code and the ESRI naming.