This guide explains how you can fix the Overwatch to launch in Fullscreen. You just need to adjust some settings of it and you will be good to go. Complete details are given below to resolve this issue.
At first, you will need to go to This PC, then Documents and open up the overwatch folder.
Now go to the Settings folder and Right click on the settings file and open up the properties.
Uncheck the Read Only option from the “Attribute” section.
Click on Apply and then tap the Ok button. Now open the Settings file and make sure that the FullScreenWindow=”1” and FullScreenWindowEnabled=”1”. Maximized Window should be “0”, Windowed FullScreen=“0” and WindowMode=”0”. Now Save and just close this file.
After saving this file, right click on the Settings file and go to properties. Now Check the Read Only option from the Attribute section. Click on Apply and then click Ok.
Now open Overwatch. When you click on “Play Now”, then it will launch in the Fullscreen Mode.
You will need to go to Options and will check that the Display Mode will be set to FullScreen.
