Way back in April of last year I wrote this post on the best way to upload images to Facebook. For a long time the method worked great. Then Facebook, being the moving target they are, changed it so that the method resulted in horribly fubared images. Trying to go back to uploading images the old way which was basically resizing them to, say, 2048px on the long side if in landscape or, if in portrait, 960px and then saving as JPEG with the sRGB color profile embedded also resulted in just horrible compression artifacts from Facebook.
This was in December of 2018 when it all went to the crapper. At that time, after much experimenting I found out that the best way to upload images to Facebook was this method, which was basically just uploading a full size and full resolution image; making sure to not optimize it in any way. It seemed that by doing so minimized the damage done by Facebook’s compression algorithm; by optimizing the image before uploading it, it essentially got hit twice, once by you, once by Facebook.
But, either way, it resulted in the best image quality, nearly equal to that of the first method.
Well, it now seems that Facebook has tweaked their algorithm once again. Now it seems that the best way to upload images to Facebook is, again, resizing them to either 2048px on the long side or 960 on the top/bottom if in portrait mode.
Originally, uploading them in PNG, i think resulted in them not being compressed at all because the algorithm seemed to only concern itself with JPEGs, but I don’t know if that’s the case.
So, at the end of the day, for best quality, it’s probably best to use the method I wrote about originally. That method is capped by saving them in PNG while preserving details. The reason I think this will work the best is because PNG is a lossless format when saving. Yes, they are converted to JPEG by Facebook, but they are only hit the one time rather than the twice it would be if you save them to JPEG before uploading them.