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What do the green lights mean on the Apple Watch and how to turn them off

The back of your device is hard at work.

Published onApril 29, 2024

An Apple Watch is a powerful fitness tracker and health-tracking tool, but how do its sensors work? One common Apple Watch problem users face is a misunderstanding of the lights on the back of their device. Find out what the green lights mean on your Apple Watch and how to turn them off.


The green lights on the back of the Apple Watch measure your heart rate. To turn off the lights, disable Heart Rate in your privacy settings.


Here’s what the green lights mean on your Apple Watch

An Apple Watch SE 2 rests face down, flashing green LED lights.
Kaitlyn Cimino / Android Authority

The green lights on your device aren’t just for flair. They serve an important role: measuring your heartbeats. Apple’s smartwatches are equipped with optical heart rate sensors, which use LED lights and light-sensitive photodiodes to determine users’ heart rates.

How it works

Human blood reflects red light and absorbs green light. An Apple Watch rapidly flashes LED lights at your wrist and measures how much light your blood absorbs. That value is lower between beats, making it possible for the device to count how many times your heart beats per minute.

Your Apple Watch uses LED lights to measure heart rate during workouts and Breath sessions and to calculate HRV. However, the sensor uses infrared light when measuring your heart rate in the background.

How to turn off the green lights

Generally speaking, the green lights should only flash during workouts, for a few minutes after workouts to record recovery data, and during breathwork sessions. If you think your sensor may be malfunctioning, try restarting your device. If you want to completely turn off the green lights, follow the steps below.

  • On your Apple Watch, open the Settings app, then scroll down to and tap Privacy & Security.
  • Scroll down to and tap Health.
  • Tap Heart Rate.
  • Tap the toggle next to Heart Rate to turn the green lights on or off.


The easiest way to keep your Apple Watch screen off is to put the device in Theater Mode. From the control center, tap the Theater Mode icon (two drama masks).

If there are green lights on the back of your Apple Watch when it is off your wrist, check to see if you have an active workout or breath exercise running.

An Apple Watch Series 4 or newer can utilize built-in electrodes to take ECG readings.

Yes. To enable sleep mode, access the control center and tap the moon icon, then tap Sleep.

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