Upload 2–4 thumbnail or cover options and see them side by side in a mock video feed and profile grid — so you can pick the one that stands out.
Preview as
Look for the one you notice first, that’s readable at small size, and that still makes sense next to the title.
Upload your options to compare them.
Make thumbnails with the Cover & Thumbnail Maker and resize images with the Social Image Resizer. The preview is a generic mock-up, not an exact copy of any app.