How To Tell If A Mirror Is Two-Way

Two-way mirrors have their legitimate applications, but unfortunately they can also be misused by bad people who seek to exploit and harm. Though relatively uncommon, two-way mirrors are sometimes installed secretly in women’s bathrooms, nightclubs, changing rooms and the like – places where people would most likely be vulnerable, and act believing that they are doing so in private.

If you suspect (or just want to make sure) that the mirror you’re facing is two-way, then there are three ways you can check.

To learn how to tell if a mirror is two-way, follow our instructions below. For all other information, see our FAQ section at the end of this article.

How to tell if a mirror is two-way (fingertip test)

  1. Press your fingertip to the mirror
  2. If you can see a gap between the end of your fingertip and its reflection, then the mirror is most likely just a regular mirror
  3. If there is no gap between your fingertip and its reflection (if they touch), then the mirror is absolutely a two-way mirror

How to tell if a mirror is two-way (sound test)

  1. Knock on the mirror like you would knock on a door
  2. If the sound of your knock sounds flat and hard, then the mirror is most likely mounted on a normal wall, and is a normal mirror
  3. If the sound of your knock is softer and hollow, then there is most likely an empty space behind the mirror, and it is probably a two-way mirror

How to tell if a mirror is two-way (torch test)

  1. Take your smartphone and turn on its torch
  2. Press the torch flat against the mirror
  3. If you can see the torchlight pass through the mirror, then it is absolutely a two-way mirror; if it does not, but simply reflects off the mirror, then the mirror is normal

Two-way mirrors are uncommon, but that doesn’t mean you shouldn’t be vigilant. If you feel unsafe, or suspect that a mirror isn’t just a normal mirror, then you can use one or all of the above tests to determine the truth for yourself. Stay safe, stay with friends, and contact the police if you think you might be in danger.

For all other information, see our FAQs below.


What is a two-way mirror?

A two-way mirror is a material which, on one side, acts as a normal mirror would – reflecting light back into the room so that you can see your reflection – whilst from the other side, the material is semi-transparent, allowing viewers to see through it. 

In other words, if two people were stood either side of a two-way mirror, person #1 would only see their reflection, whilst person #2 would be able to see person #1 as if they were looking through a window.

Two-way mirrors are most commonly used by law enforcement in interrogation rooms. If you’ve ever watched a police drama in which a suspect is being interrogated in a room with a mirror, then you’ve probably seen other police officers watching that suspect from the other side of the mirror, without the suspect’s knowledge.

Why would I want to know if a mirror is two-way?

Unfortunately, the reality of two-way mirrors being available on the global market is that they are sometimes put to illegal and dangerous use. Most commonly, in this scenario, two-way mirrors are installed in women’s bathrooms, changing rooms, and in other areas where patrons of the establishment would be led to believe that they were acting in private.

Of course, that’s not to say that all female-gendered bathrooms or changing rooms have two-way mirrors installed. Thankfully, the practice is pretty rare. Nevertheless, there are those who would seek to exploit private areas for profit – most commonly charging patrons to spy on people (usually women) whilst those people conduct themselves in private (using the bathroom, getting changed, etc.).

What should I do if I know a mirror is two-way?

If you have used one or several of the methods described above to determine whether a mirror is two-way, and you believe it is, then you should contact the local police authorities. If the mirror has been legally installed, then you have nothing to worry about; otherwise, the police will hopefully make the appropriate arrests and so ensure that the mirror is removed and the place becomes safe for patrons again.

Are two-way mirrors legal?

Two-way mirrors themselves are perfectly legal. Where legality becomes an issue is when considering where and how two-way mirrors are installed. If they are installed in a place generally considered private, and/or without your knowledge of their installation, then the likelihood is that they are illegal and being used in a harmful way. On the other hand, two-way mirrors used by police in police stations, or in clubs which make their patrons explicitly aware of their existence, are most likely legal.