Does privacy window film work at night?

Frost does: it blocks the view day and night. Reflective film doesn't: the mirror effect works when it's brighter outside than inside, so it reverses in the evening when your lights are on.

This is the most important question to ask before choosing. For a bathroom, bedroom or ground floor window used in the evening, frost is usually the right choice. For a living room where privacy matters mostly during the day, a reflective film keeps the view, and a blind or curtain takes over at night.