YouTube API now sets custom thumbnails on Shorts

What this means for you

A thumbnail is the small picture people see before they tap a video. Until now, apps could pick that picture for normal YouTube videos but not for Shorts. Now they can do it for Shorts too, once YouTube has finished getting the Short ready. So the tool you schedule with may soon let you choose a Short's cover image.

The details

• Method: thumbnails.set "now supports uploading custom thumbnails for YouTube Shorts after video processing is complete."
• Timing: call it after the Short has finished processing, not in the same step as the upload.
• Resource change: the thumbnails resource has a new shortsAspectRatio property for Shorts custom thumbnails.
• File size: thumbnails.set accepts files up to 50MB since September 2026 (our entry). YouTube Help recommends 2160 x 3840 (9:16) for Shorts thumbnails; sizes are on the YouTube hub.
• Not stated: any change to quota cost.

What to do next

• Business owners: Nothing.
• Marketers and agencies: Ask your scheduler whether it will add custom covers for YouTube Shorts.
• Developers: After a Short's processing finishes, call thumbnails.set with a 9:16 image, and read the new shortsAspectRatio property on the thumbnails resource.