While rebooting an iPhone 7 or iPhone 7 Plus requires pressing and holding both the Sleep/Wake and Volume Down buttons for at least 10 seconds, until the Apple logo appears, restarting an iPhone 8 or iPhone 8 Plus takes three steps.
The change appears to have been made because, on iPhone 8 and iPhone 8 Plus, pressing and holding the Side aka Sleep/Wake button and one of the Volume buttons now activates the Emergency SOS feature.
Keep in mind that Apple now refers to the Sleep/Wake button as the Side button as of the iPhone 8, iPhone 8 Plus, and iPhone X.
How to Force Restart or Hard Reset the iPhone 8 and iPhone 8 Plus
- Press and quickly release the Volume Up button.
- Press and quickly release the Volume Down button.
- Press and hold the Side button (aka power) until you see the Apple logo.
Force restarting an iPhone is different than recovery using DFU mode, for which the steps remain the same as the iPhone 7 and iPhone 7 Plus.