This article will go over how to change your YouTube Shorts thumbnails, whether that is while uploading your short or after. YouTube doesn’t allow you to directly add custom thumbnails; however, there is a workaround.
Since YouTube doesn’t allow you to add custom thumbnails directly, you will have to add the thumbnail you want to your actual video's first frame for about half a second (if you can, try to make it shorter than this; that way there is a lesser chance of the viewer experience being impacted). Now, you can select this frame with the methods below to still get a custom thumbnail.
First, go to the YouTube mobile app (not YouTube Studio) and upload your edited short as you would normally do (click the plus in the middle of the bottom bar and add the short). Then, once you get to the “Add Details” screen, your video's current thumbnail will be on the top left, with a pencil icon being on the top left of your thumbnail. Click the pencil icon, and then you can change your thumbnail to any frame of the video or change it to the frame of your custom thumbnail.
You can still change your shorts thumbnails even if you have already uploaded them (however, make sure you follow the “How to Add Custom Thumbnails” section of this article, or else you will need to reupload the video). Go to your YouTube channel page (click the “You” icon on the bottom of the YouTube app, then click the “View channel” button that is near the top left of the screen), go to the Shorts tab, and find the shorts thumbnail you want to edit. Then click the 3 dots on the top right of that short's thumbnail, click "Edit," then click the pencil icon on the top left of the current short's thumbnail. Finally, find the frame of your custom thumbnail, then select that.
Adding a custom thumbnail to your YouTube Short can only be done through mobile at the current time. First, make sure your thumbnail is in the first frame of your video for a split second. Next, if uploading your short, click the pencil icon on the “Add Details” screen, then select your custom thumbnail. If you already uploaded your short, go to the Shorts tab of your YouTube channel, click the three dots on the top right of your desired short, then click the pencil icon and select your custom thumbnail. If you want a thumbnail editor to make custom YouTube Shorts thumbnails, check ours out; it's designed for speed and ease of use so you don’t have to spend the whole day making your thumbnail.