How to do UI right on Mobile?

Every time I have worked on a project that deploys to Android (never tried iPhone, but assume the issue applies there as well) I have issues getting the UI to look right on the device. Even after arranging my UI and setting u anchors for everything, everything ends up smaller than I expect. I end up having to arrange to UI such that it is impossible to test the app on my computer or through unity remote, and even then this only works for a single screen resolution. Can someone explain to me how to set up the UI such that it will look correct no matter the device resolution?

I think you might be using constant physical size for the canvas.

Try making your canvas to automatically scale according to screen height and then set its reference resolution to whatever fits your assets best. This works fine for pretty much all mobile resolutions.

EDIT: If the reference resolution is set correctly, you can click Image component’s “set native size” to make it look as it was intended. Meaning that on a canvas with reference resolution height as 512, and image file with height 256 will always fill half the screen vertically.