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An Apple Watch has a green light that shines on your wrist to measure your heart rate. It does this by using the blood flow in your body and then shows you how many times your heart beats in one minute.
Why Apple Watches Use Greenlight
Given the disposition of features and functions that defines Apple Watches it is important to understand in order for them to work for you, there has to be a medium, a machine, and an algorithm. If the smartwatch is keeping an eye on your movements for Fall Detection it is not doing it at its whim or will, it has been made to do it that way.
There is a sensor placed within that keeps track of physical changes and provides the data to an algorithm to culture it into meaningful information, and just like that sensor the Green Light at the back of your Apple Watch is doing the same.
Apple Watches flashes Green Light on your wrist to record the Heart Rate of your body. It is a method to extract data using the blood flow in your body and then process it to present it in the form you expect to see: Heart Beat Per Minute (More about BPM).
But How?
Greenlight & It’s Need Defined!
Apple Watches uses PPG technology (photoplethysmography) to determine the heart rate of a person. It works by shining a light into the skin to detect changes in blood volume, which occur with each heartbeat. The sensor then uses algorithms to translate this information into a heart rate measurement.
Quite simple, isn’t it? Unless you are wondering why Green Light? Why not Blue or Purple or Orange light? They could’ve used anything, right?
In one word: No!
Greenlight is specifically chosen because it has a wavelength that can penetrate the skin and reach the blood vessels, allowing for accurate measurement of heart rate. Additionally, green light is less likely to be absorbed by other tissues, reducing interference and improving the accuracy of the readings.
Is Greenlight Harmful For Us?
No.
While PPG method itself has its pros and cons that can sway your opinion either way, occasional or even frequent exposure to Green Light isn’t dangerous to your skin. You don’t need to worry about it.
| Pros | Cons |
| The sensors do not require any skin penetration or contact with the body, making it a convenient and safe option for monitoring heart rate. | Although the accuracy of optical heart rate sensors has improved, it can still be limited, especially during high-intensity physical activities. |
| Optical heart rate sensors in smartwatches provide continuous, real-time monitoring of heart rate, which is useful for tracking fitness and health. | External factors such as ambient light and skin pigmentation can impact the accuracy of optical heart rate sensors. |
| The sensors are integrated into wearable devices such as smartwatches, which makes it easy to monitor heart rate on the go. | In order for the sensors to work effectively, it is important for the smartwatch to maintain good contact with the skin, which can be difficult during certain activities. |
| With advances in technology, optical heart rate sensors in smartwatches have become more accurate and reliable in recent years. | The continuous use of optical heart rate sensors can impact the battery life of a smartwatch, requiring more frequent charging. |
Apple Watches (like Fitbit and many others in wearable industry) tends to use PPG because of many factors. Yet the most obvious of which is that it is incredibly easy to implement it – even if there is delicate issue of accuracy. Either way, it shouldn’t be forgotten that at the end of the day these are only wearables trying to imitate the medical devices. You don’t need to put your 100% faith in their ability.
“Can I Use Greenlight On My Apple Watch For Any Other Thing?”
To be fair, there is one use that comes to mind. If and when you would have to find your Apple Watch and you’d try to locate it using your iPhone. Upon the call, your Apple Watch can chime as well as light up with Green Light to make it easier for you to find it.
Needless to say this can happen even if you’d have switched off the Heart Rate tracking. Speaking of which do you want to assume control of Green Light on your Apple Watch?
How Turn On Or Off The Greenlight
In order to put an end to Green Light on any Apple Watch the only viable option is to axe the Heart Rate function. Which does make perfect sense Green Light is after all used to capture the reading for it.
To do it through the Apple Watch:
- Press Digital Crown
- Go To Settings
- Click On Privacy & Security
- Select Heart Rate
- Toggle It Off
To do it by MyWatch app on your iPhone:
- Go To The MyWatch
- Navigate To Privacy
- Toggle Off Heart Rate
Other Method Apple Can Use To Track Heart Rate?
Apart from the PPG method that is currently being used there are few other options that Apple can invest in their future smartwatch line up. However, it should be noted that at the time the most cost efficient way to track heart rate is the one that is being currently used.
With that being Apple Watch Series 4, Series 5, Series 6, Series 7, Series 8, or Ultra2 also have built-in electrodes in the Digital Crown and the back of Apple Watch, which can measure the electrical signals across your heart when used with the Heart Rate app or the ECG app. When you place your finger on the Digital Crown, it creates a closed circuit between your heart and both arms, capturing the electrical impulses across your chest.
To use the electrical heart sensor to measure your heart rate, open the Heart Rate app and place your finger on the Digital Crown. You will get a faster reading with higher fidelity — getting a measurement every second instead of every 5 seconds.
“My Apple Watch Also Shines Redlight? What Does It Do?”
If you have also seen your Apple Watch shining Redlight then this is for you, because it is quite common to get confused between the two lights. While Greenlight on your Apple Watch is indicator of heart rate tracking. The Redlight is all about SPO2 or simply the monitoring of oxygen level in your blood. It is completely different metric with completely different purpose.
So if you see your Apple Watch with redlight at it’s back, don’t assume it is warning you of blowing up. No, it simply means that your smartwatch is trying to find out the oxygen-blood ratio of your body.
Frequently Asked Questions
Yes it does.
While in workout mode Heart Rate sensors is ON so it is possible that is why Greenlight is On.
Your Apple Watch uses green and red lights to track heart rate and SPO2.
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