In a web map, I can rotate the basemap to a freehand angle by right-clicking the map, holding, and dragging.
That works, but it's fiddly to get a map with grid-shaped roads to be rotated to a perfect vertical orientation. Is there a way to rotate the map to a known angle instead, by entering something like 18.5 degrees?
Related AGOL idea: Rotate web map by angle
I'm not sure if there's a way to enter a specific angle, but I did want to share that you can use the keyboard shortcuts A and D when the map view is in focus to rotate the map. Perhaps that would be easier than dragging with a mouse?
If you're comfortable editing your web map's JSON, you can find the rotation property under initialState / viewpoint / rotation.