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Learn how your Apple Watch uses light to measure your heart rate
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Have you noticed the green lights on the bottom of your Apple Watch and wondered what they are—or wondered how you can turn them off? The green lights on your Apple Watch are used to check your heart rate, but they can be turned off if they're annoying or you think they may be why your Apple Watch battery dying too fast . In this article, we'll explain what these lights do, how they work, and how you can disable them.

Apple Watch and Green Flashing Lights

The lights flashing on your Apple Watch are the heart rate sensor. They can be disabled in your watch's settings, but this will also disable the heart rate monitor.

Section 1 of 4:

Why Your Apple Watch Has Flashing Green Lights

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  1. These lights periodically flash when you're wearing your Apple Watch to measure your heart rate. These lights can be disabled by turning off the watch's heart rate sensor. There's no way to keep the heart rate sensor on and also turn off the green lights.
    • According to Apple, this is called "photoplethysmography," which works around the fact that blood is red and absorbs green light. [1]
    • The amount of blood flowing in your wrist increases and decreases with the beating of your heart. This also affects how much green light is absorbed from the sensors on the back of your Apple Watch, which is how it can measure your heart rate.
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Section 2 of 4:

Disabling the Lights via Your Apple Watch

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  1. The Settings app has a gray icon with gears on it.
  2. This will open privacy settings relating to what health metrics your watch can gather.
  3. This will disable the green light sensors on the bottom of your Apple Watch.
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Section 3 of 4:

Disabling the Lights via Your iPhone

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  1. The Apple Watch app has a dark gray icon with an image of an Apple Watch on it.
  2. You may have to scroll down to see this option.
  3. This will disable the green light sensors on the bottom of your Apple Watch.
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