This article explains how to turn off the screen of an Apple Watch and how to completely turn off the device. Unlike the iPhone, it is not possible to turn off the screen of an Apple Watch by pressing a button.
Steps
Method 1 of 2: Turn off the screen
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Step 1. Make sure you are wearing the Apple Watch on your wrist
The device screen lights up (or "wakes") automatically when you lift your wrist and face it (while wearing the Apple Watch).
If you're not wearing the Apple Watch, place it on a flat surface. This way the screen should turn off automatically
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Step 2. Lower your wrist
In most cases, you will simply have to lower your wrist or hold it motionless for a few seconds to have the Apple Watch screen turn off automatically.
If this fails, turn your wrist 45 degrees away from you
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Step 3. Try taking the Apple Watch off your wrist
If your device screen doesn't turn off, try removing the Apple Watch from your wrist and placing it on a flat surface.
Method 2 of 2: Turn off the Apple Watch
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Step 1. Activate the Apple Watch screen
Lift your wrist or press one of the buttons located on the right side of the device.
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Step 2. Press and hold the "Power" button
It has an oval shape and is placed along the right side of the Apple Watch. Some options will appear.
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Step 3. Drag the "Power Off" slider to the right
It is displayed at the top of the Apple Watch screen.
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Step 4. Wait for the Apple Watch to turn off
The screen should turn off immediately, but the Apple logo may appear on screen for a few moments before this happens. At this point the Apple Watch is completely turned off.