Recently, it has come to our attention that users may experience the Facebook stream with different aspect ratios. On some of them, it displays with a 16:9 ratio and some with a 4:3 ratio. It appears that Facebook has changed the aspect ratio depending on what device you are watching from and whether you are watching on a timeline or in the actual post itself. It is just the way Facebook has decided to deliver videos to the user in different scenarios. This will only affect the viewers on Facebook, it will not affect viewers on your website, Roku, Apple Tv etc.