So this is going to be a very short post
Because this changes all the time.. almost annually.. I’m just gonna point you THE BEST online reference I found on the Social Pilot website. Here is the link.
They have a quick graphic that lists image dimensions for the top social media platforms, and they drill down to the granular level specifics: Stories, versus Ads, versus Events, yada yada.
Social Pilot keeps this info updated regularly, they give you tips on all-important file sizes, solid advice to upload images as sRGB JPG file to avoid any compression and so much more. This page has saved me hours of tedious research, and I hope it helps you, too!
And now, my work here is done.
A++ work, Social Pilot! Thank you!