Why is the rearview mirror blue?

As drivers, we depend heavily on our rearview mirrors to navigate roads safely. While using the mirror, you may have wondered why it sometimes appears to turn blue.

I’ll explain what causes your rearview mirror to turn blue and how this feature works.

What Causes a Rearview Mirror to Turn Blue?

A rearview mirror turns blue when it has a light sensor that triggers an auto-dimming feature, designed to reduce the amount of light reflected in your direction from oncoming headlights or bright sunlight shining in your car.

How Does the Auto-Dimming Feature Work?

The auto-dimming feature consists of a light sensor and a mirror with an electrochromic material layer. The sensor detects the amount of light entering the car and sends signals to the electrochromic layer of the mirror.

When there’s high intensity in external lightings, such as headlights at night, this will trigger sensors attached above or inside of vehicles’ normal mirrors (rear-view & side mirrors), and they’ll darken according to certain regulations set for these systems.

The reflection from lights passing through this new darkened lens will then be less intense now that more overall light energy has been absorbed by materials within its structure—it essentially attenuates infrared radiation wavelengths between 800-1000 nm by about 70%.

Importance of Having an Auto-Dimming Mirror

An auto-dimming mirror, also known as an electrochromic mirror, is a valuable feature in modern vehicles. It provides several benefits for drivers, enhancing both safety and convenience. Some of the key advantages of having an auto-dimming mirror include:

  1. Glare reduction: The primary function of an auto-dimming mirror is to reduce glare from the headlights of trailing vehicles, which can impair a driver’s vision and cause discomfort. By automatically adjusting the reflectivity of the mirror, it helps maintain clear visibility and reduces eye strain, making nighttime driving safer and more comfortable.
  2. Enhanced safety: With reduced glare, drivers can better focus on the road and their surroundings, lowering the risk of accidents caused by visual distractions. Furthermore, auto-dimming mirrors eliminate the need to manually adjust the rearview mirror, allowing drivers to keep their hands on the steering wheel and their attention on driving.
  3. Improved comfort: Auto-dimming mirrors help create a more comfortable driving experience, especially during nighttime or in low-light conditions. They minimize the annoyance and discomfort caused by the bright lights from trailing vehicles, making it easier to concentrate on the road ahead.
  4. Adaptive to changing conditions: An auto-dimming mirror automatically adjusts its reflectivity based on ambient light conditions. This means that it will always provide the optimal level of glare reduction without any input from the driver, ensuring consistent visibility and comfort.
  5. Reduced eye fatigue: Constantly adjusting to the changing brightness of headlights from other vehicles can be tiring for the eyes. Auto-dimming mirrors help reduce eye fatigue, allowing drivers to stay more alert and focused on the road.
  6. Increased vehicle value: Auto-dimming mirrors are a desirable feature for many car buyers, and having one installed in your vehicle can increase its value and appeal.
  7. Aesthetic appeal: Many auto-dimming mirrors have a sleek, modern design that adds a touch of sophistication to your vehicle’s interior.

Moreover, the glare reflects so much that it can blind or disorient drivers temporarily. Auto-dimming mirrors come into play here by reducing this danger and improving road safety.

How to Check if Your Car Has an Auto-Dimming Mirror

You could check your vehicle’s mirror for a small rectangular window glass attached to the mirror itself; this is where the light sensor for the auto-dimming feature resides.

During daytime driving, the reflections from objects behind your vehicle appear normal. However, at night, the bright headlights from oncoming traffic can become more intense.

To manage this, auto-dimming mirrors adjust their dimming levels based on your preset preferences. These electronic controls are typically found close to the driver’s seat, either on the dashboard above the steering wheel or on a button on the door panel.

This allows you to easily adjust the brightness of the mirror for a more comfortable driving experience.


A blue-tinted rearview mirror isn’t unusual; it’s actually a sign that the auto-dimming feature is working effectively. The blue tint helps block strong light reflections, which can impair visibility and affect road safety.

So, if you haven’t installed an auto-dimming mirror in your car yet, think about adding one to enhance your driving experience and stay safer on the road!

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