Typography

On a thumbnail, type competes with everything else in a crowded feed at a size smaller than a business card, so the decisions get brutal. Heavy weights survive scaling down and thin ones vanish. Contrast against whatever sits behind the letters matters more than the typeface you picked. A stroke or a drop shadow separates text from a busy background, though a thick outline on already-heavy type turns words into blobs. On-screen text inside the video has a different constraint. It has to be readable in the time it is up, and it has to stay clear of the area where captions and the progress bar live.