X/Twitter Maximum file size: Up to 5MB for photos and GIFs on mobile. Up to 15MB on the web.
Different sources say different things for FB, but i found a max of 30MB on a few more recent sites.
LinkedIn 8MB
Pinterest 20MB
YouTube Banner image 6MB
Snapchat 5MB
… just a quick research 🖖🏼👁🤙🏼