What is the difference in zoom levels in Map Viewer and Map Viewer Classic when a tile layer is used?

Answer

There is a difference in behavior regarding zoom levels between Map Viewer and Map Viewer Classic when a tile layer is used as a custom basemap. Map Viewer prevents zooming in past the maximum level of detail for the tile layer, or zooming out past the minimum level of detail.

However, when opening the same web map in Map Viewer Classic, we can zoom in past the tile layer's maximum level of detail, and zoom out past the minimum level of detail. Although this is past the maximum level of detail for the tile layer, we are still allowed to zoom in even further. However at this point, Map Viewer Classic resamples the closest available tile to the current level of detail to display the basemap, resulting in blurriness. Likewise, Map Viewer Classic allows zooming out past the minimum level of detail.

In Map Viewer, the available zoom levels for the web map are based on the "minLOD" and "maxLOD" parameters in the basemap tile layer's JSON. In this case, zooming out past a level of detail of 10 (Scale = 1:577,790.554289) is prohibited, and zooming in past a level of detail of 11 (Scale = 1:288,895.277144) and is also prohibited, as shown in snippets of the JSON below:

{"wkid": 102100,"latestWkid":3857}},"minScale":0.0,"maxScale":0.0,"minLOD":10,"maxLOD":11,"tileInfo":
...
{"level":10,"resolution":152.874056570411,"scale":577790.554289},{"level":11,"resolution":76.437028250732,"scale":288895.277144}
...

In Map Viewer Classic, the available zoom levels for the web map are based off all the levels of detail in the tiling scheme for the basemap tile layer, even if there are no tiles available for those levels of detail, as shown in the following JSON:

{"x":-9497963.94301857,"y":9997963.94301857},"spatialReference":{"wkid":32612,"latestWkid":32612},"lods":
[{"level":0,"resolution":78109.09330483258,"scale":2.952154707584223E8},
{"level":1,"resolution":39054.54665241629,"scale":1.4760773537921116E8},
{"level":2,"resolution":19527.273326208146,"scale":7.380386768960558E7},
{"level":3,"resolution":9763.636663104073,"scale":3.690193384480279E7},
{"level":4,"resolution":4881.818331552036,"scale":1.8450966922401395E7},
{"level":5,"resolution":2440.909165776018,"scale":9225483.461200697},
{"level":6,"resolution":1220.454582888009,"scale":4612741.730600349},
{"level":7,"resolution":610.2272914440045,"scale":2306370.8653001743},
{"level":8,"resolution":305.1136457220023,"scale":1153185.4326500872},
{"level":9,"resolution":152.55682286100114,"scale":576592.7163250436},
{"level":10,"resolution":76.27841143050057,"scale":288296.3581625218},
{"level":11,"resolution":38.139205715250284,"scale":144148.1790812609},
{"level":12,"resolution":19.069602857625142,"scale":72074.08954063045},
{"level":13,"resolution":9.534801428812571,"scale":36037.044770315224},
{"level":14,"resolution":4.7674007144062855,"scale":18018.522385157612},
{"level":15,"resolution":2.3837003572031428,"scale":9009.261192578806},
{"level":16,"resolution":1.1918501786015714,"scale":4504.630596289403},
{"level":17,"resolution":0.5959250893007857,"scale":2252.3152981447015},
{"level":18,"resolution":0.29796254465039285,"scale":1126.1576490723508}]},"documentInfo":