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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.
January 26, 2023

An Apple Watch is a powerful health-tracking tool, but how do its sensors work? Find out what the green lights mean on your Apple Watch and how to turn them off if needed.

Read more: Everything you need to know about Apple’s wearables


The green lights on the back of the Apple Watch are used to 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 actually serve an important role: measuring your beats. Apple Watches equip optical heart rate sensors. These sensors use LED lights and light-sensitive photodiodes to determine users’ heart rates.

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

The watch uses LED lights to measure heart rate during workouts and Breath sessions as well as to calculate HRV. When measuring your heart rate in the background, however, the sensor uses infrared light.

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 the device. If you want to turn off the green lights completely, 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.

Read more: Common Apple Watch problems and solutions


An Apple Watch Series 4 or newer can utilize built-in electrodes to take ECG readings. Learn how to use the Apple Watch ECG app with our dedicated guide.

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.