YouTube thumbnails will show up in different sizes across YouTube and embedded player outside YouTube. Just like YouTube video specs for uploading, uploading YouTube thumbnail also has some standard YouTube thumbnail dimensions that you need to know.
1. YouTube thumbnail resolution: 1280 x 720 pixels. That means 1280 pixels wide and 720 pixels tall. The minimum width of the thumbnail should be 640 pixels.
2. YouTube thumbnail size: your thumbnail image file must be kept under the 2MB limit. Any greater and YouTube will reject your upload.
3. YouTube thumbnail format: .jpg, .gif, .bmp, or .png.
4. YouTube thumbnail aspect ratio: The aspect ratio is the width of the image relative to its height. 16:9 is the standard aspect ratio in YouTube players and previews.
Now, I believe you can upload a YouTube thumbnail with the right size. If you think that the thumbnail you made is not beautiful enough, some thumbnail maker for YouTube is also worth recommending. If this article helps you solve the YouTube video thumbnail size problem, don't hesitate to share it with more people.