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While using your Apple Watch, you may have noticed some flickering green light on the watch's underside. You might want to know what that green light is and its function or usefulness to humans.

This blog post will explain the green light and provide further information about it. Read on.

What is the green light on the Apple Watch?

While wearing an Apple Watch, you may notice that it suddenly glows green. The green light is produced by the optical LED, which helps to measure measures your heart rate.

But why green? Well, it's because of a technology called photoplethysmography. And while that may sound complicated, the concept is relatively simple.

Blood appears red since it reflects red light, absorbs most of the green light, and reflects a little of it. The heart sensor uses green LED lights to flash on your skin, and light‑sensitive photodiode sensors detect reflections that measure the amount of blood flowing through your wrist.

When your heart beats fast, the blood flows in your wrist — and the green light absorption — is more significant. When it's slow, light absorption is less.

The green light flashes hundreds of times per second. At that speed, our eyes can't discern individual flashes, and the light appears solid green. But each flash of the LED serves as a snapshot of your blood flow.

Put hundreds of these snapshots together, and the Apple Watch can figure out when your heart is beating and calculate your heart rate.

But if you've ever felt like the green light is way brighter than usual, there's a reason for that too. If the heart sensor can't detect your blood flow due to a weak signal, it's designed to brighten the green light and increase the flashing speed to compensate.

Making the glow more noticeable than usual. This typically happens if you're wearing a looser band or if your wrist is in a particular position that prevents the watch from making contact with your skin.

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How to turn on the green light on Apple Watch

  • Go to the Apple Watch apps.
  • Open up your heart app on the watch and tap on the right.
  • That's it. Simple.

Why does my Apple Watch turn green when I'm not wearing it?

Many Apple Watch users have complained that their Apple Watch flashes the green light even when they are not wearing it. The reason is that the green light on the bottom surface of the Apple Watch is used to measure your heart rate intermittently. The lights will remain on anytime the heart rate measurement procedure is complete.

Even when you're not using the Workout or Heart Rate app, your Apple Watch will frequently check your daily rate. According to Apple:

"Apple Watch measures your heart rate throughout the day when you're still, and periodically when you're walking. Since Apple Watch takes these background readings based on your activity, the time between these measurements will vary. Apple Watch also calculates a daily resting rate and walking average by correlating background heart rate readings with accelerometer data when sufficient background readings are available."

Underside of an Apple watch showing the LEDs that flash the green light

What if the green light on Apple Watch is not working

These actions below could be helpful:

  • Navigate to the My Watch app on your iPhone.
  • Then to Workout on your iPhone's Watch app.
  • If it's on, disable the Workout Power Saving Mode.
  • Then go to Settings.
  • Navigate to Privacy.
  • Tap on Motion and Fitness on your iPhone and make sure that both Fitness Tracking and Health are turned on.
  • Verify that the Activity app is configured correctly.
  • Ensure that daily activity can be tracked.

How to make my Apple Watch stop blinking?

Some people may not feel comfortable keeping the green light blinking and may want to turn it off. If necessary, you can go to the watch's settings and turn off the heart rate monitoring because the only way to turn off the green light is to turn off the monitor. To do that, follow the steps below:

  • Restart your Apple Watch.
  • Open the Watch app on your iPhone.
  • Scroll down the screen and tap on Privacy.
  • Turn off heart rate and fitness tracking.
  • Turn on power-saving mode.
  • That's it.

Can Apple watch give a false heart rate?

Yes, the Apple watch can give a false heart rate if it is not worn or fitted correctly on the wrist. A loosely fitting band that moves around or has notable gaps between the Watch and the skin can cause an inaccurate reading.

Apple Watches are designed to be worn in a firm grip on the wrist and in close contact with the skin so that the LED green light can easily obtain health data readings from the skin on the wrist.

Wearing them loose or without a good fitting will prevent the sensors underneath the watch from obtaining accurate readings when the green LED light is being flashed.

Proper way to wear an Apple watch to obtain accurate readings

Does the Apple Watch green light determine if stand or seat?

No, the Apple Watch only uses the green light to obtain changes in blood flow, which it uses in heart rate measurements.

To resolve if you are sitting or standing, the Apple Watch uses an accelerometer and motion sensors to understand your body movement.

Frequently Asked Questions about Apple Watch green light

Q. How accurate is the heartbeat measured on the Apple Watch?

A. The heartbeat measure on the Apple Watch is relatively accurate as it is integrated with technology that can detect your pulse.

Q. How do smart watches measure the heartbeat on the wrist?

A. The heart rate monitor is based on photoplethysmography technology. This technology uses green LED lights paired with light-sensitive photodiodes to illuminate your skin and measure changes in light absorption. This helps the device to detect the amount of blood going through your wrist at any given moment, hence your heart rate.

Q. What is the green light on the front of my Apple Watch?

A.  According to Apple, the green light on the front of the watch determines an individual blood flow on the wrist at any given time. This technology is based on the fundamental observation that "blood is red because it absorbs and reflects red and some green light."

Q. Should the green light always be on Apple Watch?

A. Seeing the green LED light on may be uncomfortable for new users because it gives the idea that something is faulty with the Apple Watch. However, there is nothing wrong with letting your green LED light on as it is useful for tracking your heart rate.

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Wrap Up

This article has explained the green light's role on the Apple Watch. New users should know that it is a technology that helps the watch measure the heart rate, which it uses in computing other health data.

If you have any questions about the green light on Apple Watch, please leave them in the comments below. Thanks for reading.

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