LinkedIn Post Image size: 1200 x 627 pixels.

LinkedIn's image specifications for Pages give 1200 by 627 pixels, a 1.91:1 ratio, for custom Page post images, require anything uploaded to be more than 200 pixels wide, and cap files at 3 MB in PNG or JPEG. That is the same shape as a link card, which is why a 1200 by 630 og:image and a 1200 by 627 post image are interchangeable in practice: the three pixel difference sits inside LinkedIn's tolerance.

A single image in the feed is shown at the column width and keeps its own ratio, so landscape, square and 4:5 portrait are all displayed uncropped. Posts carrying two or more images switch to a collage that crops each one to a square or a 4:3 tile, so a graphic with type near an edge belongs in a post of its own. The desktop feed column is only about 550 pixels wide, which means 1200 pixels is plenty of resolution and type below roughly 28 pixels tall stops being readable.

Landscape is the right choice when the picture supports the writing: a chart, a screenshot, a quote card under a long post. When the image is the post, a 1080 by 1350 portrait takes nearly twice the screen height at the same width, and it is a separate entry in this reference.