I got my first mirror film from Ali express and applied it to the outside of the window. During the day its like a mirror from the outside. But when its dark, you can see through the window. The Gardinia film from Galaxus was applied to the inside of the window. It was used to cut down light and heat in a room used as an office. It had the same effect. You can see out of the window no problem. I never looked into the room from the outside because its on the 3rd floor. There are many good videos to watch on YouTube which are helpful.