Does one way window film work at night?

How one way film works

One way, or mirrored, film is a reflective film. Whichever side is brighter sees its own reflection, and whichever side is darker can see through. On a sunny day the outside is far brighter than the room, so passers-by see a mirror while you can see out.

Why it stops working at night

Once it's dark outside and the lights are on inside, the room is the brighter side. Now you see your own reflection in the glass, and people outside can see in. The film hasn't failed. It's how reflective films behave.

What works for privacy at night

• Frosted or etched film. It blocks the view in both directions, day and night, while still letting light through. It's the right choice for bathrooms and ground-floor rooms used in the evening.
• Gradient or banded film. Frosted where you need privacy, usually the lower part of the glass, and clear above for light and sky.
• Reflective film plus a blind. Daytime privacy and the view from the film, with a blind or curtain closed in the evening.
• Dual reflective film. Has a less mirrored finish on the inside, so you see less of your own reflection at night. It still doesn't give night-time privacy on its own.