Here's how to optimize each:Square Posts: Stick to a 1080 x 1080 px size with a 1:1 aspect ratio. ... Landscape Posts: For a wider view, go with 1080 x 566 px and an aspect ratio of 1.91:1. ... Portrait Posts: To capture more vertical space, use 1080 x 1350 px with a 4:5 aspect ratio.