Can you tint a window so that no one can see in, but everyone can see out?

Method 1: It depends on the amount of light on the inside compared to the outside. If there is a lot of light inside, for example, a well-lit office space, this will be very hard to make invisible to the outside if the outside is a darker area without any exposure to sunlight. It will be also hard to get full visibility out the window because of reflective issues. If a customer is adamant about this type of set up, you can go with a one-way mirror type film. Reflective films rather than dark films will be more effective at allowing visibility from the inside, so go for shininess instead of darkness.