Canvas is a short, looping visual that plays behind a track on the Spotify mobile app — a separate asset type from your cover art or a music video.
4.6.1 What Canvas is
A looping visual (typically a few seconds) attached to a specific track, visible to listeners on Spotify's mobile app during playback. It is distinct from both static cover art (2.2) and a full music video.
4.6.2 Content standards
Spotify maintains a dedicated Canvas content policy separate from its general music content rules — review current Canvas-specific guidelines via Spotify for Artists before uploading.
Source: MadDesk article 4.6 (4-6)