Limits and SizesYouTube's help page "Add custom thumbnails on YouTube" says that custom thumbnails for Shorts can currently be added only in YouTube Studio on a computer, and your account must be verified. For uploaded files, the recommended aspect ratio is 9:16. The page does not state a pixel size, so we do not either; use the 9:16 shape and a high resolution such as 1080 x 1920 as a safe choice.
Read on 14 November 2026 at support.google.com/youtube/answer/72431. Apps can change a limit without notice; check the app before an important post.
Making the picture
Use the resizer with the Shorts thumbnail option to crop your picture to 9:16. Put the main subject and any words in the middle. Keep the words few and large.
A note on older advice
You will find many articles that give a fixed pixel size for video thumbnails. The page we read does not give one, so check YouTube Studio when you upload.
Questions people ask
Where do I add a Shorts thumbnail?
Per the help page, in YouTube Studio on a computer, and the account must be verified.
What size should the picture be?
The page gives only the shape, 9:16. A tall picture such as 1080 x 1920 is a sensible choice.