Samsung
Power Off a Samsung Device auf Samsung
On many Samsung phones the side key is now shared with Bixby. A short press wakes the screen, but a long press can launch the assistant instead of the shutdown menu. This is why the classic press-and-hold method sometimes fails on newer One UI devices, even though it still works on older models.
If your device supports the classic method, the path is straightforward: Press and hold the Power button ➔ Tap on Power off ➔ Tap again on Power off. The second tap is required as a safety confirmation, so a single tap on the first screen will not shut the phone down.
When the power button is bound to Bixby, use the status bar instead. Swipe down from the top of the screen to open the quick panel, then tap the power icon shown there to reach the same Power off confirmation screen.
Choose the status bar method whenever holding the button only opens Bixby or the screen stays unresponsive. If the display is completely frozen and neither method reacts, a forced restart is the safer fix rather than repeating the shutdown attempt.