YouTube appears to be testing image ads on mobile during horizontal video playback. Instead of just traditional video ad breaks, the platform displays a static image ad that overlays part of the screen. It doesn’t interrupt or cover the video.

Observers have indicated that these image ads appear roughly every three minutes during playback, creating a more frequent interruption than with previous ads YouTube was using.
This update could introduce a new inventory option for advertisers while significantly changing the viewing experience for mobile users.
It remains unclear whether this is a limited experiment or the beginning of a broader rollout.
This update was spotted by Hana Kobzová.