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The green lights on the back of your Apple Watch are its optical heart-rate sensor. They use green LEDs and light-sensitive photodiodes to detect blood-flow changes in your wrist and estimate your heart rate. To disable them completely, go to Settings → Privacy & Security → Health → Heart Rate and turn off Heart Rate. This also stops Apple Watch from collecting heart-rate data and disables related features.
What the green lights do
Apple Watch uses a technique called photoplethysmography (PPG). As your heart beats, the amount of blood in your wrist changes. Blood absorbs and reflects light differently depending on its volume, so the watch’s photodiodes measure the reflected green light and use the pattern to estimate beats per minute.
![Apple Watch Series 11 [GPS 42mm] Smartwatch with Rose Gold Aluminum Case with Light Blush Sport Band - S/M. Sleep Score, Fitness Tracker, Health Monitoring, Always-On Display, Water Resistant](https://m.media-amazon.com/images/I/31caPPnRysL._SL160_.jpg)
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The lights are not cameras, notification indicators, or a sign that the watch is recording video. They are part of the normal optical heart-rate sensor on the underside of the case. Seeing an occasional flash—especially in a dark room—is generally normal.
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- During workouts: Heart rate is measured continuously during a Workout session.
- After workouts: The watch may continue measuring for up to three minutes to calculate heart-rate recovery.
- In the background: Apple Watch takes periodic readings while worn. The timing varies with activity and other conditions.
- During Breathe and Reflect sessions: These sessions can use the heart-rate sensor.
- For health and fitness calculations: Green-light readings contribute to metrics such as walking average and heart-rate variability (HRV).
- In third-party fitness apps: Running, cycling, gym, sleep, and similar apps can request heart-rate data. Workout sessions can generate high-frequency readings, as explained in Apple’s developer documentation.
The lights are easier to see when the watch is loose, not flush against your wrist, or briefly active after you remove it. Visibility alone does not mean the sensor is faulty.
#1 Best Overall
![Apple Watch Series 11 [GPS 46mm] Smartwatch with Jet Black Aluminum Case with Black Sport Band - M/L. Sleep Score, Fitness Tracker, Health Monitoring, Always-On Display, Water Resistant](https://m.media-amazon.com/images/I/416RQ0rtsUL._SL160_.jpg)
- A FULL-FEATURED HEALTH TRACKER—Apple Watch Series 11 gives you invaluable insights about your body, right from your wrist. Take an ECG anytime* and get alerts for a high and low heart rate or an irregular rhythm*—so you can stay closer to your heart. You can also view your overnight health tracking metrics with the Vitals app* and be notified of possible sleep apnea.*
- KNOW YOUR SLEEP SCORE—With advanced sleep tracking, Series 11 gives you a daily sleep score. It’s an easy way to help measure and understand the quality of your sleep, so you can make it more restorative.
- GET HYPERTENSION NOTIFICATIONS—Did you know that Series 11 can spot signs of chronic high blood pressure? By analyzing how your blood vessels respond to beats of the heart, it can notify you of possible hypertension.*
- SAFETY FEATURES—A smartwatch that puts your safety first. Series 11 can detect a hard fall or severe car crash, automatically help connect you with emergency services, and notify your emergency contacts.* Check In can automatically notify a loved one when you’ve arrived at your destination.
- A POWERFUL FITNESS TRACKER—With advanced metrics and motivating features like Pacer, Heart Rate Zones, training load, and Workout Buddy powered by Apple Intelligence from your nearby iPhone*—Series 11 is made to help everyone stay active, from runners and hikers to strength-training enthusiasts.
How to turn the green lights off completely
- Open Settings on your Apple Watch.
- Tap Privacy & Security.
- Tap Health.
- Tap Heart Rate.
- Turn off Heart Rate.
Apple also documents an iPhone route through Watch app → My Watch → Privacy → Heart Rate, although labels and menu nesting can vary between watchOS and iOS versions.
A less drastic option: Low Power Mode
If your goal is to reduce sensor activity or extend battery life rather than permanently disable heart-rate tracking, try Low Power Mode:
- Control Center: Press the side button, tap the battery-percentage button, then turn on Low Power Mode.
- Settings: Open Settings → Battery → Low Power Mode.
According to Apple’s support documentation, Low Power Mode disables background heart-rate measurements and several heart-rate notifications, including irregular-rhythm, high-heart-rate, and low-heart-rate notifications. It also changes other watch functions, such as Always On display behavior, and can reduce or alter some workout measurements.
Rank #3
![Apple Watch SE 3 [GPS 40mm] Smartwatch with Starlight Aluminum Case with Starlight Sport Band - S/M. Fitness and Sleep Trackers, Heart Rate Monitor, Always-On Display, Water Resistant](https://m.media-amazon.com/images/I/31YiTby0pOL._SL160_.jpg)
- GET SMARTER HEALTH INSIGHTS—Apple Watch SE 3 is an advanced health tracker that helps you better understand your body. The smartwatch sends alerts for an irregular heart rhythm, or an unusually high or low heart rate.* You can view your overnight health tracking metrics with the Vitals app,* track your sleep score, and get sleep apnea notifications.*
- A GREAT FITNESS TRACKER—SE 3 can track your workouts in a healthy number of ways—from running and strength training to simply achieving your 10K steps a day. With real-time metrics and Workout Buddy powered by Apple Intelligence from your nearby iPhone,* you’ll hit your goals like never before.
- KEEP HELP CLOSE AT HAND—SE 3 is a smartwatch that can detect a hard fall or severe car crash and automatically help connect you to emergency services and notify your emergency contacts.* Check In can automatically notify a loved one when you’ve arrived at your destination.
- WOMEN’S HEALTH INSIGHTS—SE 3 has advanced sensors that track your wrist temperature while you sleep. With this smartwatch, you can log your periods and symptoms, get period predictions, and get notified of cycle deviations.*
- GREAT BATTERY LIFE AND FASTER CHARGING—Enjoy a smartwatch with all-day, 18-hour battery life* from sunup to sundown. Then charge up to twice as fast as SE 2* and get up to 8 hours of battery in just 15 minutes.*
Low Power Mode is therefore a broad battery-saving setting, not a dedicated way to hide the green LEDs. It may not prevent every sensor activation when you deliberately open a heart-rate or workout feature.
If the green lights stay on
Occasional flashes are expected, but illumination that appears continuous or unusually persistent deserves a few checks. Try these steps in order:
Rank #4
![Apple Watch SE 3 [GPS 40mm] Smartwatch with Midnight Aluminum Case with Midnight Sport Band - S/M. Fitness and Sleep Trackers, Heart Rate Monitor, Always-On Display, Water Resistant](https://m.media-amazon.com/images/I/31Gq8SToFJL._SL160_.jpg)
- GET SMARTER HEALTH INSIGHTS—Apple Watch SE 3 is an advanced health tracker that helps you better understand your body. The smartwatch sends alerts for an irregular heart rhythm, or an unusually high or low heart rate.* You can view your overnight health tracking metrics with the Vitals app,* track your sleep score, and get sleep apnea notifications.*
- A GREAT FITNESS TRACKER—SE 3 can track your workouts in a healthy number of ways—from running and strength training to simply achieving your 10K steps a day. With real-time metrics and Workout Buddy powered by Apple Intelligence from your nearby iPhone,* you’ll hit your goals like never before.
- KEEP HELP CLOSE AT HAND—SE 3 is a smartwatch that can detect a hard fall or severe car crash and automatically help connect you to emergency services and notify your emergency contacts.* Check In can automatically notify a loved one when you’ve arrived at your destination.
- WOMEN’S HEALTH INSIGHTS—SE 3 has advanced sensors that track your wrist temperature while you sleep. With this smartwatch, you can log your periods and symptoms, get period predictions, and get notified of cycle deviations.*
- GREAT BATTERY LIFE AND FASTER CHARGING—Enjoy a smartwatch with all-day, 18-hour battery life* from sunup to sundown. Then charge up to twice as fast as SE 2* and get up to 8 hours of battery in just 15 minutes.*
- End the Workout session: Open the Workout app and end, discard, or save any active workout. Leaving a workout paused may not be enough.
- Check third-party apps: Look for an active session in running, cycling, gym, sleep-tracking, or other fitness apps.
- Wait a few minutes: The watch can continue taking readings for up to three minutes after a workout while calculating recovery.
- Clean and dry the watch: Wipe the back of the watch and your wrist. Sweat, water, dirt, a loose fit, cold skin, and tattoos can affect optical readings. Apple recommends a clean, dry watch and proper fit for reliable measurements; see its Heart Rate user guide.
- Restart the watch: A restart can clear a sensor or app session that has not closed correctly.
- Install watchOS updates: Update the watch if a compatible update is available.
- Contact Apple Support: Seek support if the lights remain active after these steps, particularly if the problem comes with rapid battery drain, overheating, failed heart-rate readings, or other sensor failures.
A light that appears after the watch has been removed can be temporary, including when the watch is coming off a charger or completing a session. It is not by itself proof of a hardware defect.
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Green lights versus red lights
| Light | Main purpose | Relevant control |
|---|---|---|
| Green | Optical heart-rate sensing | Settings → Privacy & Security → Health → Heart Rate |
| Red | Blood Oxygen measurements on supported watches and in supported regions | Settings → Blood Oxygen |
Apple describes Blood Oxygen measurements as using a bright red light—not the green heart-rate LEDs. On supported models, background recordings can be adjusted under Settings → Blood Oxygen by turning off In Sleep Focus and In Theater Mode. Those controls affect background measurements in those modes and do not necessarily disable every on-demand Blood Oxygen reading.
Best Value
![Apple Watch Series 11 [GPS 42mm] Smartwatch with Jet Black Aluminum Case with Black Sport Band - S/M. Sleep Score, Fitness Tracker, Health Monitoring, Always-On Display, Water Resistant](https://m.media-amazon.com/images/I/41s72HIk5TL._SL160_.jpg)
- A FULL-FEATURED HEALTH TRACKER—Apple Watch Series 11 gives you invaluable insights about your body, right from your wrist. Take an ECG anytime* and get alerts for a high and low heart rate or an irregular rhythm*—so you can stay closer to your heart. You can also view your overnight health tracking metrics with the Vitals app* and be notified of possible sleep apnea.*
- KNOW YOUR SLEEP SCORE—With advanced sleep tracking, Series 11 gives you a daily sleep score. It’s an easy way to help measure and understand the quality of your sleep, so you can make it more restorative.
- GET HYPERTENSION NOTIFICATIONS—Did you know that Series 11 can spot signs of chronic high blood pressure? By analyzing how your blood vessels respond to beats of the heart, it can notify you of possible hypertension.*
- SAFETY FEATURES—A smartwatch that puts your safety first. Series 11 can detect a hard fall or severe car crash, automatically help connect you with emergency services, and notify your emergency contacts.* Check In can automatically notify a loved one when you’ve arrived at your destination.
- A POWERFUL FITNESS TRACKER—With advanced metrics and motivating features like Pacer, Heart Rate Zones, training load, and Workout Buddy powered by Apple Intelligence from your nearby iPhone*—Series 11 is made to help everyone stay active, from runners and hikers to strength-training enthusiasts.
Blood Oxygen availability varies by model and region. Apple documents support for Apple Watch Series 6 or later and all Apple Watch Ultra models, subject to restrictions. In the United States, certain watches purchased on or after January 18, 2024 have results analyzed on the paired iPhone and displayed in the Health app. See Apple’s Blood Oxygen availability information. Apple says Blood Oxygen readings are for general fitness and wellness, not medical use.
Can you keep heart-rate tracking while hiding only the LEDs?
Apple does not provide a separate cosmetic setting that suppresses only the visible green light while leaving all heart-rate functions active. The practical choices are to leave Heart Rate enabled and accept normal sensor activity, end unnecessary workouts, use Low Power Mode with its broader limitations, or turn off Heart Rate entirely and lose the associated readings and features.
