How to lock aspect ratio on full screen

I’ve created a game in a 3:4 aspect ratio, it is a portrait format.
If I set the window (mac) to full screen, the game is stretched to the full width of my monitor. I would like to lock my 3:4 aspec ratio, so when I toggle full screen the game stays in the middle inbetween “blank” borders.

Edit>Project Settings>Player>Supported Aspect Ratios

http://wiki.unity3d.com/index.php?title=AspectRatioEnforcer

Hi rjth!

In Build Settings > Player Settings > Resolution and Presentation
you can check on [Default is full screen] ✓ and then check off [Default is native resolution].

Then you can set up width and height in pixels so its not aspect ratio, but for some it might be helpful.

The YouTube app for Android mobile automatically adapts the player to the size of the video. Whether it’s vertical, square, or horizontal, the video will fill the screen Official Website. The vertical (portrait) video player matches the aspect ratio of the video - getting taller for square and vertical videos, and shorter for widescreen videos.