The Facebook Feed Post size (1200×630px)
1200x630 pixels at 1.91:1 is the workhorse size for Facebook feed images and shared link previews. Facebook renders link thumbnails at this ratio, so matching it means your shared articles and posts display as a full, edge-to-edge banner instead of a cramped or padded thumbnail.
This size threads the needle between desktop and mobile. On desktop the feed column is wide, and on mobile it stretches nearly full width, so a 1200-pixel-wide image stays crisp in both without triggering Facebook's aggressive downscaling and recompression that hits oversized uploads hardest.
A frequent mistake is packing the image with text. Facebook favors mostly visual creative, and dense on-image copy shrinks to an unreadable strip on phones. Keep any text short and centered, and remember that when a link preview collapses to a smaller card on some placements, the sides can be trimmed, so keep logos and key messaging away from the far edges.