Device type

YouTube Analytics reports views by the hardware people watched on. It matters because the same thumbnail is a postage stamp on a phone and a poster on a living room screen, and because watch behaviour differs by device. Watch time on TV screens has overtaken mobile, and TV viewers tend to sit with longer videos than viewers elsewhere. If a large share of your audience is on a television, small text and fine detail in a thumbnail are wasted effort, and so is any line of script that assumes the viewer can tap something.