Facebook – How to Set Uploaded Videos to Play in HD by Default

Go to your FB "Account settings". there will be an option "Timeline and Tagging" in the left side. click on this tab. then some option will appear in the right side. Go on the "Who can see things on my timeline?" option. After select "Who can see what others post on your timeline?" select friends and or Everyone. I hope this was your question " how to show your post on timeline by default.

There are two option available to play the youtube video and you need to select one

(i) Always choose the best quality for my connection and player size

(ii) I have a slow connection. Never play higher-quality video

This can be seen in the setting page by going to settings -> playback and it is applicable for globally.

If you have chosen the 1st option,then video would be played in hd mode.

There is choice in the playing video you have option to chose the pixel size.This is saved temporarily so if you refresh it would revert back to the default option and your selection would be unchecked so this is reason why it went back to 1080 p since you have select the 1st option.