Overwatch always opens in windowed mode?

In the settings I change it to fullscreen but everytime I start the game it still defaults to open in windowed anyways. Is there some way to change that?

I've found people who have had a similar issue here. The solution (temporarily until Blizzard sort it out) seems to be:

1. Go to your Overwatch game settings (Documents -> Overwatch -> Settings).
2. Delete your settings file.
3. Launch the game, change settings to full screen.
4. Go back to your settings file, right click and set it to read only.

Seems overwatch doesnt like other programs with overlays, programs that always makes me enter in windows mode

1) Teamviewer 2) MSI Gaming app 3) Mumble overlay

There might be others, but try to check if any running programs have overlays.