Add Rounded Corners to Thumbnails

Thumbnails with rounded corners have become a popular design trend in YouTube, blog posts, and card-based UI components. The softened corners make thumbnails look more polished and modern, and they stand out compared to sharp-rectangle images in search results and recommendation feeds.

For thumbnails at 1280×720 px (YouTube standard), a corner radius of 20–40 px creates the standard modern card look. Larger radius values (80–120 px) create a more distinctive "pill" shape that stands out even more in a thumbnail grid.

Export as PNG to preserve the transparent corners. The thumbnail will then display correctly on any background — whether in a white-background browser, a dark-theme YouTube page, or a custom website with a coloured background.