Understanding the Red Light Under Your Apple Watch: 1 Minute to Discover Why Your Apple Watch Has a Red Light

Many Apple Watch users have noticed a mysterious red light shining underneath their device—especially at night or when checking their pulse. If you’re curious about what this red light means, rest assured it’s a normal part of your watch’s advanced health monitoring features. The red light you see is actually an array of LEDs that help measure your blood oxygen levels. Apple introduced this sensor starting with the Series 6, and it plays a crucial role in keeping tabs on your well-being by shining red and infrared light into your skin, then analyzing how much is reflected back to estimate the oxygen saturation in your blood. This technology allows the Apple Watch to perform spot checks or background tracking, and no action is needed on your part. The light won’t harm you, nor does it indicate anything is wrong with your device—it’s simply doing its job behind the scenes.

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FAQ

Q: Why does my Apple Watch have a red light underneath?

A: The red light is part of the blood oxygen sensor, used to monitor your blood oxygen saturation levels by shining light into your skin and measuring the reflection.

Q: Is the red light on my Apple Watch dangerous?

A: No, the red light is completely safe. It’s an LED used for noninvasive health measurements, and it does not harm your skin.

Q: Can I turn off the red light on my Apple Watch?

A: You can disable background blood oxygen measurements in the Health app’s settings, which will prevent the red light from activating automatically.

Q: Does every Apple Watch have the red light sensor?

A: No, only models starting with Apple Watch Series 6 and newer have the blood oxygen sensor and accompanying red/infrared LEDs.

Q: What else are the lights on the back of my Apple Watch used for?

A: Apart from the red/infrared LEDs for blood oxygen measurement, green LEDs are used for heart rate monitoring, working in a similar way by detecting blood flow.