If Your Apple Watch Emits a Green Light, It's for a Good Reason

If you have an Apple Watch, you've definitely encountered the infamous bright green light. What is it? What does it do? Here's what we know.

Allison DeGrushe - Author

Apr. 7 2022, Published 6:12 p.m. ET

Those of us who sleep with our Apple Watches are sometimes jolted out of our beauty sleep by a glowing green light on the verge of blinding us. You could honestly just be lounging on the couch watching TV, and a neon glow will suddenly radiate from the back of your device.

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So, what does the green light even do on an Apple Watch? Here's everything we know, including how to turn it off.

A row of Apple Watches at the Apple Store.
Source: Getty Images
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What does the green light do on an Apple Watch?

According to Apple, the green LED lights are used by the optical heart sensor known as photoplethysmography (we're not even attempting to pronounce that word). The company states that this technology is based on the simple fact that "blood is red because it reflects red light and absorbs green light."

As a result, the Apple Watch employs green LED lights alongside light‑sensitive photodiodes to detect one's blood flow through the wrist at any given time. The technology giant notes that "when your heart beats, the blood flow in your wrist —and the green light absorption — is greater." But "between beats, it’s less."

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Additionally, Apple Explained shared a two-minute clip on YouTube detailing the green LED lights. The account revealed that although we assume the lights are glowing, they are actually flashing "hundreds of times per second." Ultimately, those flashes serve as snapshots of our blood flow — how cool is that?!

Here's how to turn off the green LED lights on your Apple Watch.

Unfortunately, the only way to completely turn off the green LED lights on your Apple Watch is by disabling the heart rate monitor in the watch's settings.

To do this, head to the Watch app on your iPhone and select "Privacy." From there, switch off the "Heart Rate" setting. Now, if you're not willing to turn off the "Heart Rate" setting, then we highly suggest you just wait it out; the green LED lights will disappear within minutes.

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