The Constant Biometric Scan
The Apple Watch features a highly sensitive optical heart sensor located on the rear ceramic crystal. By default, this sensor is active 24/7. Even when you are not working out, the watch silently fires its green LEDs every few minutes to calculate your resting heart rate and monitor for irregular rhythms. While this is an excellent health feature for many users, physically firing an optical array hundreds of times a day consumes a significant amount of battery life. If you only care about notifications and do not want continuous biometric tracking, you must paralyze this sensor.
How to Turn Off Background Heart Rate Measurements
You can permanently sever the background biometric daemon via the Privacy settings.
- Open the Settings app directly on your Apple Watch (the grey gear icon).
- Scroll down the main list and tap on Privacy & Security.
- Tap on Health.
- Tap on Heart Rate.
- Locate the master toggle switch labeled Heart Rate.
- Toggle this switch to the Off position (the green background will disappear).
Absolute Sensor Blackout
The change is instantaneous. The Apple Watch will completely sever the bridge connecting the background health daemon to the optical hardware array. The green LEDs on the back of the watch are now permanently deactivated. You can sit still, sleep, or walk around, and the operating system will absolutely refuse to record your pulse. This provides absolute biometric privacy and immediately unlocks a massive amount of reserve battery life, as the watch is no longer forced to execute continuous, power-hungry optical calculations.