The Medium Article Header size (1500×750px)
A Medium article header, the featured image at the top of your story, works well at 1500x750 pixels in a 2:1 ratio. This image sets the tone as readers open your piece, and Medium also pulls it into article previews and cards, so it doubles as the thumbnail that draws clicks in feeds and publication pages.
Because the featured image appears both large at the top of the article and cropped smaller in preview cards, keep the focal subject centered so it survives the tighter crop. A clean, editorial image with a clear point of interest reads better than a busy composition, matching Medium's minimal, reading-focused aesthetic.
If the header includes text, keep it centered and large, since preview crops can trim the edges and small type disappears at thumbnail size. Upload at the full 1500x750 so the image stays crisp on wide screens where Medium displays it large, while still looking sharp when reduced to a card, covering both the in-article and preview contexts.