Youtube puts a black border around my video?

throwaway12341241

Commendable
May 11, 2016
1
0
1,510
When I upload a video to Youtube it puts a black border around my video, making it not take up the maximum size available. Is there a setting to make it so it does take it the maximum?
 

BZRKturbo

Commendable
May 10, 2016
59
0
1,610


This is all spot-on but it could also be the device you are watching it on..... my phone isn't 16:9 AR so it puts black bars there (on normal videos like youtube ect.).