YouTube thumbnail dimensions and upload file limits
Choose the thumbnail's actual content type and upload device before exporting. YouTube's current guidance recommends different canvases for videos and Shorts, and separates desktop from mobile file limits. A file that fits one route is not automatically appropriate for another.
Choose the intended canvas
| Thumbnail use | Current recommendation | Minimum dimension or ratio |
|---|---|---|
| Video | 3840 × 2160 pixels | Minimum width 640 pixels; 16:9 recommended |
| Short | 2160 × 3840 pixels | Minimum height 640 pixels; 9:16 recommended |
| Podcast playlist | Square artwork | 1:1 rather than 16:9 |
Keep upload-route limits separate
| Route in YouTube's guidance | Reported file limit | Practical check |
|---|---|---|
| Mobile video thumbnail | Under 2 MB | Inspect the final exported file |
| Mobile podcast thumbnail | Under 10 MB | Do not apply the video's smaller limit by default |
| Desktop video, Short or podcast thumbnail | Under 50 MB | Use the actual desktop upload route |
Check the current upload and display route
The help page names JPG and PNG and says custom Shorts thumbnail upload is available through desktop Studio with a verified account. For vertical videos, a 16:9 custom image can be replaced by an automatic 4:5 preview on Home, Explore and subscription surfaces. Review the surface viewers actually use.
The dimensions are recommendations, not a reason to stretch a small source image and assume detail has improved. Prepare a canvas that preserves the intended subject, export it, then inspect the resulting pixels and file size. The linked local image checker accepts files up to its own 20 MB limit; that is a Boostsy tool limit, not YouTube's desktop limit.
Review the export in context
Identify the actual destination
Record whether this image is for a video, Short or podcast playlist and whether the upload will happen on desktop or mobile.
Preserve the useful subject
Check faces, products, labels or the comparison the viewer needs to understand. Changing the canvas ratio by stretching the image can distort that subject.
Inspect the final file
Measure the exported file rather than a design application's estimate. Confirm its dimensions and supported format; retain the original editable artwork separately.
Review the published preview
Check the actual viewing surfaces and phone-size readability. If the thumbnail promises a particular answer, make sure the video supplies it.