Yes, one-way privacy window films do not work at night. In particular, people will be able to see inside if the room is illuminated. If you are looking for a one-way window film that works at night, there is one available called Contra Vision® White 24/7 Concealed Vision™. This creates a similar one-way vision effect as net curtains during daytime. At night time, the window film is partially illuminated by the light from inside and this helps to obscure the view. However, the positioning of the light inside is important. The more diffused, the better. Curtains and blinds are still needed if you want strong privacy. If you need strong 24/7 privacy, you need a frosted or stained glass product which also blocks the view for people inside the room.