And if you want a perfect fullscreen for you game and it could also help with your loading time issues, you don't need to launch the game on a new tab on itch.io. You just need to add a little more height to your game on itch.io than you added to your game in Unity. For example, I chose a resolution of 960x600 for my game in Unity and 960x650 on itch.io. This allowed space for the Unity's full-screen banner just below my game window. Have a nice day!