Why does picture and video quality diminish when uploaded to Facebook?

I have an iPhone 7 Plus and the picture and video quality is really great. But when I post them to Facebook, the quality diminishes. The pictures and videos aren't nearly as clear as they are in my camera roll. Is there a reason why and is there a way I can fix that?

Facebook has a high quality option, but it's buried. To enable it, create a new photo album. While you're creating the album, check the box that says "High Quality." Now, any photos that are uploaded to this album will be stored in larger, less compress file sizes.

You can't fix that Cell Phone Pictures will only look good on your Phone when you Upload them to Facebook it will lose some of its Quality when you Upload it onto Facebook because the Pictures are on the Smaller Screen you can't always see the bad Quality but its in there but when it gets Uploaded to Facebook the Size is Resized and that causes it to lose the Quality

  • Why does the video quality look bad when uploaded to the computer? [iPhone 4]? When I upload my video to youtube in HD directly from the iphone, I go on the computer to watch it on youtube and the quality is perfectly normal. But when I copy the file from my iphone and onto my computer the video looks grainy? I wan't to put it into after effects and do some editing but how can I go about KEEPING the quality of the video? I don't get why it gets all grainy when I put it onto my computer vs. It being perfect when I upload it directly from my ipod to youtube?
  • Why does my video have such bad video quality? I uploaded my video to the computer and it had great video quality, then I uploaded it to Facebook and YouTube and It looked horrible. It there anything I can do to change that? Save it a different way or something? I see all these YouTube videos that have been filmed by iPhone's and they have great quality. Shouldn't my 14mp camera have even better!
  • Why does my iPhone receive good quality videos as bad quality videos? So I recently met a famous guy in concert and when I got a picture wth him I was getting a video and my friend used her phone to video it. So she sent it to me and it was like terrible quality and the video was like little with a huge black border around it. But yet it looks perfectly fine on her phone? How do I fix it? Whenever I try to get video editing apps it always says error & only with that particular video. I have an iPhone 5c, and so does my friend.
  • Why does my iPhone 4s have poor video quality? Whenever I take a video and upload it from my phone to my computer, the video is distorted; it skips every once and a while and it is sort of pixel-y. It never used to do this and it looks fine on my phone, but not the computer. Any ideas on what is wrong? I'm uploading it to iPhoto