YouTube’s new guidelines recommend that creators upload images at 2120 X 1192 px so that all designs will scale appropriately for desktop and mobile viewing. A channel’s banner will now be able to stretch and constrict depending on the size of the browser window it is being viewed in.
The minimum width of channel banners is 1280 X 350 px with the maximum being 2120 x 350 px. The below template provided by YouTube shows the “safe area” of a logo, which will not be cut off by a low resolution display or smaller browser window.
Logos will also scale accordingly with mobile devices and tablets. Again, if you stay within the “safe area” your logo will show up without any problems during mobile viewing.
Below you can find a cheat sheet for channel art guidelines:
Recommended image size: 2120 X 1992 px
Desktop max size: 2120 x 350 px
Desktop minimum: 1280 x 350 px
Tablet size: 1536 X 350 px
Mobile size: 1280 X 350 px