How to spot a double sided mirror?

A double-sided mirror is often used to create an illusion of depth or for privacy. Find out how to tell if a mirror is one-way or two-way and the differences between them.

what is a double sided mirror?


You would’ve seen films or TV shows where a police officer interrogates a suspect in a room with a large mirror, behind which other officers watch the interrogation or saw warnings about similar mirrors being present in changing rooms in stores or public bathrooms. These strange glasses are called two-sided mirrors, double-sided mirrors, or one-way mirrors.

On one side of the two-way mirror glass, a person will be able to see their reflection, while on the other side, it will be a tinted window. If you want to learn more about two-way mirrors, the usage of such mirrors, or the two-way mirror test, which is a test to figure out if a normal-looking mirror is a double-sided mirror, keep reading! 

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What is a two-sided mirror?

Two-way mirrors have many other names. They are known as double-sided mirrors, two-way mirrors, or two-way glasses; but, funnily enough, they are also sometimes called one-way mirrors or semi-transparent mirrors. This might be because while such mirrors or glasses are used from both sides, only one side is reflective but since they are useful on both sides, they are more commonly called double-sided or two-way mirrors.

The way these two-way mirrors are made is similar to how regular mirrors are made, that is, with a coating of metal on glass. The only difference is that two-way mirrors are made with an even thinner, almost transparent coating on metal, which allows some of the light to pass to the other side.

what is a two sided mirror

This is the reason why rooms or areas on the non-reflective side of two-way mirrors are kept dark and rooms on the reflective side are brightly lit to make all the light reflect from the mirror.

People are often told to beware of two-way mirrors in places requiring some level of privacy but are accessible by the general public such as changing rooms in stores, public bathrooms, hotel rooms, etc. they are also frequently represented in movies or TV shows in scenes in interrogation rooms in police stations and observation rooms in laboratories but that being said, it is not all that double-sided mirror glasses are useful for.

Uses of double-sided mirrors

So here are some of the more ways double-mirrors are used in our daily lives:

1. Mirror TV

A mirror TV is the name of an amazing invention that is appropriately named as it can be both a mirror and TV and it does so with the help of two-way mirrors or semi-transparent mirrors. This television uses the basic concept of how two-way mirrors work, which is that one side needs to be dark and the other, brightly lit.

A television screen is hidden behind a two-way mirror with the reflective side on the outside and while the television is turned off, the glass will reflect like a normal mirror. When the television is turned on the brightness from the screen will reduce the reflectiveness of the glass and allow the screen to be seen from the outside.

Ideally, the lighting in the room should be bright when the mirror TV is to be used as a mirror and dim or dark when it is to be used as a television.

2. Teleprompters

double sided mirror teleprompter

Teleprompters are devices that display text or a script for a speaker to allow them to simply read the text on the screen without having to memorize their speech. Teleprompters usually use a kind of a two-way mirror that has almost no tint to its non-reflective side, allowing people on that side to perceive the glass as a regular transparent sheet of glass.

When the glass is placed at an angle, a screen displaying text or the speech is placed below the reflective side of the glass, allowing the text to be reflected back and the speaker being able to look at the text to read. Several variations of teleprompters have come up and are considered especially useful in reality TV or for TV presenters.

A video camera is placed behind the glass that captures the presenter while they are read from the text on the reflective side, without having to look away, memorize their script, or use cue cards to speak.

3. Smart or Virtual Mirrors

smart double sided mirror

A Smart Mirror is seemingly a normal mirror, but it can also display information such as the time, date, current weather, social media updates, etc. and uses two-way mirrors to function.

A screen displaying all the information is placed behind the glass on the non-reflective side while the reflective side acts as a regular mirror. Glasses meant to be Smart Mirrors are specially made to be more reflective than transparent so that only the information meant to be displayed on the mirror is seen while the rest of the glass reflects back the image like a mirror.

They can even have LEDs to act as a lighting source or be touch or voice-activated.

4. Mirrored Sunglasses

double side mirrored Sunglasses

Mirrored sunglasses have normal lenses with a thin layer of reflective, metallic coating on the outside but work as transparent but tinted glasses on the inside, thus effectively preventing all the glare from reaching the eyes and giving the viewer a clear vision with minimal eyestrain.

The outside is often coated with vibrant colored coating, giving a unique appearance to the wearer of the sunglasses as well. These sunglasses are considered very useful for sports and outside activities as it reflects away all the glare and harmful rays of the sun on the reflective side and prevents them from reaching the eyes.

It is the reason why many professional athletes tend to wear mirrored sunglasses while performing.

double sided makeup mirror

It is important to note that a certain kind of makeup mirror is known as double-sided makeup mirror or double-sided handheld mirror, but these are not true two-way mirrors but merely have a regular magnifying mirror on either side so that a person can see a close-up view of their face.

5. Security Cameras

double sided mirror security camera

It is common to hide security cameras behind two-way mirrors. A popular way of doing so is using dome-shaped two-way mirrors. The reflective side is placed outwards and the transparent side on the inside with a camera inside it.

The dome shape allows the camera to capture a 360 degree view while remaining somewhat concealed inside the two-way mirror.

6. Mirrored Windows

One-way mirrored windows are frequently seen nowadays on buildings and houses with large glass windows. Since two-way mirrors are reflective on one side and transparent on the other, the reflective side could be on the outside, giving people on the inside full privacy as outsiders will only see their reflection and not anything on the inside.

types of two sided mirrors

These kinds of one-way mirrors are made especially to act as windows, usually being more reflective than transparent and tempered to strengthen the glass or made with two-way mirror acrylic glass. However, a two-way mirror film can also be applied to regular transparent glass to make it reflective on one side and transparent or semi-transparent on the other.

An added advantage of having mirrored windows is that they provide protection from harmful UV rays; these are made with a low-emissivity coating and are also often used in automobiles.

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What are the differences between one-sided and two-sided mirrors?

While two-way mirrors are also called both one-sided and two-way mirrors, they are more commonly known and referred to as two-way mirrors as that accurately describes their function. So technically, there isn’t any difference between one-sided and two-way mirrors.

However, there is a lot of difference between a regular mirror and a two-sided mirror. A two-way or two-sided mirror is one that is reflective on one side and transparent on the other, and a regular mirror is reflective on one side and completely opaque on the other. Therefore, this forms the basic difference between the two kinds of mirrors.

Let’s look at some of the other ways these mirrors are different from each other:

  • Coating

A regular mirror is a piece of transparent glass coated with a thick metallic coating that can be up to 99% reflective, which also makes it practically opaque from the non-reflective side.

On the other hand, two-way mirrors are made by applying a very thin metallic coating which is not as reflective and is also semi-transparent on the other side, which may appear tinted.

  • Lighting 

For an image to appear on a normal mirror, the lighting in the room is irrelevant. However, with a two-way mirror, it is essential in almost every case that the lighting on the reflective side be very bright, or at least enough to overpower the amount of lighting on the non-reflective or transparent side.

Thus, the non-reflective side should be only dimly lit or in complete darkness. If it is not, the other side of the two-way mirror will not be as reflective.

  • Placement

Regular mirrors are often placed or installed on a wall like in bathrooms or on cabinets. We can easily see where the mirror meets the wall and look behind it by removing it from its place through some or the other process.

Conversely, two-way mirrors are, in most cases, a part of the wall itself as in the case of mirrors in interrogation rooms or on buildings as windows. (Source)

Different ways to spot a two ways mirror

We’ve talked about the ways in which regular mirrors and two-way mirrors are different from each other in their building and placement, as well as what effect lighting has on the two of them.

Different ways to spot a two ways mirror

That being said, there are a few other ways you can figure out if the mirror in front of you is a two-way mirror or a regular mirror. This can come in handy if you are suspicious of there being a two-way mirror in places meant to be private such as public bathrooms, changing rooms in stores, and hotel rooms.

So here are different ways to spot a two-way mirror:

1. The Fingernail Test

The fingernail test is perhaps the most well-known test to check if a normal-looking mirror is a two-way mirror. To conduct this test, all you have to do is place your fingernail against the glass. If there is a gap between your fingernail and its reflection in the glass, then it is definitely a regular mirror.

On the other hand, if there seems to be no gap between your fingernail and the reflection, then there is a chance that it might be a two-way mirror. However, this test is not very reliable as it can give different results based on the angle of the mirror and lighting in the room so it is always advised to conduct more tests and look for other ways to tell if the mirror in front of you is a two-way mirror.

2. Check the lighting in the room

We know that two-way mirrors work on the principle that the lighting in the area on the reflective side of the glass should be brighter than that on its non-reflective or transparent side. As soon as the lighting on the reflective side becomes any less brighter than it is or is taken away completely, you will be able to see through the glass on the other side.

Thus, see if you can turn off the lighting in the room to check whether the glass is a regular mirror or not, in case you are worried about your privacy.

3. Blocking out lighting

This method can be used if there is no way that you can turn off the lights in the room or dim them to try and spot a two-way mirror. All you have to do is press your face close up against the mirror and use your hands by cupping them around your face and blocking out the light. You can also use any clothes or similar material you have on hand to block out the light.

Once you do so, if the mirror truly is a two-way mirror, it will become less reflective and you will be able to somewhat see the other side. If it is a normal mirror, you might just see darkness.

4. Location of the mirror

While it is illegal to have two-way mirrors where people would expect privacy, they can sometimes be placed in public for unique advertisement or surveillance purposes. However, it is required by law for these mirrors to have a sign or notice of any sort to inform the public that what they are looking at is, in fact, a double-sided mirror.

If you suspect that there is a two-way mirror in a private place or room such as a locker room, bathroom, hotel room, changing room, etc. then inspect thoroughly and let the authorities know immediately.

5. Using a flashlight

If all of the above tests to spot a transparent mirror turn out to be inconclusive, you can also use your smartphone and its flashlight feature to check the glass. Since the lighting is already bound to be bright on the reflective side of the glass, shining a flashlight directly at the mirror and making it even brighter in a concentrated place will make the light pass through the glass and to the other side.

Thus, if it is not a regular mirror, then you will be able to see to the other side but if it is a genuine mirror, then the only thing you will see in the glass is the reflection of the flashlight.

5. Knocking on the mirror

Two-way mirrors are meant to be used from both sides unlike regular mirrors, which are only meant to be used from the reflective side because the other side is opaque and usually fixed against a wall. Using this knowledge, we can figure out whether a mirror is genuine or not.

Knocking on the glass in front of you will generate a hollow, ringing echo if it is a semi-transparent mirror as there will be space behind the glass, whereas the sound of knocking on a regular mirror will be a dull thud. To have a better idea of the distinction between the two sounds, imagine knocking on a window as opposed to knocking on a tiled wall.

List of websites where you can buy a two-sided mirror from

If you are looking to buy two-sided or transparent mirrors for home projects such as a Mirror TV, Smart Mirror, etc. then you can easily buy some in the required dimensions from your local glass or mirror store but there are also a few options to buy these online. Some of them have been mentioned below:

  • Amazon

Amazon is a great website to look for one-way mirror film for windows in your house. These options are great for privacy purposes, easy on the pocket, and also easy to install. Installing a one-way mirror film to your windows will make the side on the outside reflective, preventing anyone from looking inside your home.

This is considered to be a brilliant option for people who live on the ground floor or have large windows they would like to prevent people from seeing through without compromising on the view.

  • Target

Target is also a website that will deliver one-way mirror film right to your doorstep. These can also be easily installed on most types of windows and prevent anyone on the outside from looking in during the day. Target also offers same-day delivery and allows you to pick up from your nearest Target store if you want to get the product immediately.

  • Two Way Mirrors

Two Way Mirrors is a website specifically devoted to manufacturing and delivering two-way mirrors all around the world.they have a very wide variety of two-way mirror-related products to choose from.

These include acrylic 2-way mirror, 2-way mirror film, teleprompter mirror, TV mirror, smart mirror, glass 2-way mirror, colored 2-way mirror, 2-way dome mirror, etc. You can decide the quantity and size or dimensions of the glass you want and even get instant prices on the website itself accordingly.

List of websites where you can buy a two-sided mirror from


Two-way mirrors are an amazing invention that allows a person to see their own image reflected back to them, just like a normal mirror, but will also allow another person to view the glass as a transparent window and be able to look through the glass without anyone on the other side knowing about it. These mirrors are used for many fun and creative purposes such as in a Mirror TV, Smart Mirror (which is a double-sided mirror with light), teleprompter, mirrored sunglasses, concealment of security cameras, etc. 

Since double-sided mirrors can also become a serious issue if they are used illegally in a place where one would expect complete privacy, there are some ways to easily spot a two-way mirror. These methods include the fingernail test, checking the placement of the mirror, knocking on the mirror, shining a flashlight directly at it, and many more.

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Frequently Asked Questions (FAQs) about double sided mirrors

What is a three-way mirror?

A three-way mirror is nothing but an arrangement of three different panels of genuine mirrors put together side by side. The two mirror panels or double-sided mirror doors on both sides can usually be adjusted in the required angles or folded over each other when not in use, with the mirror panel on the center remaining fixed. For this reason, the three-way mirror system is also called the tri-fold mirror design. These mirrors have come up as an interesting tool to assist someone in cutting their own hair because this arrangement allows a person to view the back of their head quite easily. However, the tri-fold mirror system has been commonly used for decades in the form of a vanity tabletop mirror as it shows every angle of your face when doing your hair and makeup in front of it.

Do two-way mirrors work at night?

A two-way mirror is a glass that is coated with a very thin layer of metal that makes the glass reflective on one side, acting like a mirror but allows the light to pass through to the other side, making that side see-through or transparent. However, this can only work if the lighting on the reflective side is much brighter than the lighting on the transparent side. If the light is not bright enough on the mirror side, then a person standing on that side will be able to see through to the other side. Thus, two-way mirrors tend not to work as intended at night if they are placed in an outdoor setting such as in the form of windows. The two-way mirror windows might prevent people on the outside from looking in during the day because of all the sunlight, but their reflectiveness will decrease as the sun sets and you have to turn the lights on inside your house, making the transparent side brighter than the reflective one. Using curtains or blinds is, therefore, recommended in this case.

How can you tell if it’s a double-sided mirror?

Since it is possible for someone to see your reflection in a two-way mirror from the other side without you knowing, the prospect of there being hidden two-way mirrors in places you would expect privacy is pretty scary. Fortunately, there are quite a few easy ways of spotting a double-sided mirror on your own:

  • The fingernail test is the most commonly known way to check if a mirror is single or double-sided. All you have to do is put your fingernail against the glass in front of you and look at its reflection in it. If there is a gap between your fingernail and its reflection, then it is a genuine mirror but if there is no gap, then it is likely that the glass is a two-way mirror.
  • Looking at how the mirror is placed in the room can give you a clue about its nature. This is because regular mirrors are attached to a wall but two-way mirrors form a part of the wall itself as there has to be an area behind the glass for observation in this case.
  • Shining a flashlight, such as the one from your smartphone, at the glass will illuminate the area beyond the glass if it is a two-way mirror. If it is a genuine mirror, then all you will see is the reflection of the flashlight.
  • Since two-way mirrors would most likely have an empty space or room behind the glass on its transparent side, knocking on the glass can also reveal whether the glass is genuine or double-sided. Knocking on a regular mirror will make a dull thud, but doing so with a two-way mirror will make a hollow, ringing sound, just like knocking on a window will make.

How do I make windows not see-through from the outside?

More and more people are now opting for two-way mirror windows for privacy and aesthetic purposes. These windows allow people on the inside to have a complete view of the outside through the window, but people on the outside will not be able to see through the glass and will only see their own image reflected back to them. If you have regular, transparent windows, you can still make your windows semi-transparent like a two-way mirror by installing a double-sided mirror tape or film.

How do you make a trifold mirror?

You can easily make your own tri-fold mirror or three-sided mirror by installing hinges on the sides of three different mirrors of the same size so that the two mirrors on both sides will move along the hinges. This kind of mirror arrangement is extremely useful for when you are doing your hair and makeup and want to look at every angle of your head easily.

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