For iPhone, you’d think that tapping and holding the right-side power button would prompt you with the reset settings, but that’s sadly not the case.
Instead, you’ll need to tap and hold both the power button and the volume down key on the left side. After three seconds, a power-off slider should appear on the screen. Swipe across to confirm the action.
Also: How to restart every iPhone ever made
For Android, tapping and holding the power button may follow a similar behavior as the iPhone, activating the built-in voice assistant instead of the reset prompt. If that happens, press both the power button and the volume down key for three seconds or until you’re given the option to power off or restart the phone.
Note: On most Android phones, you’ll have the ability to modify your power button so that it triggers the reset options by default instead of the voice assistant. You can’t do this on an iPhone though.

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https://www.zdnet.com/article/why-you-should-restart-your-phone-on-a-regular-basis-and-how-to-do-it/