Apple's newest range of smartphones, iPhone 11, iPhone 11 Pro and iPhone Pro Max, share the same overall design as Apple's 2018 devices. In the absence of a home button, they also inherited the same method of forcing a quick restart.
Un forced restart of the new iPhones involve pressing the side buttons in a special combination, and while it's not immediately obvious once you learn the steps, it's the quickest way to restart your iPhone if it crashes:
- Quickly press and release the Volume Up button;
- Quickly press and release the Volume Down button;
- Press and hold the side button until the Apple logo appears, then release the side button.
During this process, you will see a slider to turn off the iPhone. Ignore it and continue holding the side button until the screen goes black. At that point, the Apple logo will appear, release any key and, when the restart is complete, the screen will activate again.
Using the forced restart process prevents you from turning off the iPhone completely, but if you want to turn off the iPhone, you can do so by going to the General section of the Settings app, scrolling down and choosing the Shut Down option. You can also hold down the Volume Up button and the Side button at the same time to bring up the Emergency SOS interface which also houses a "slide to power off" option.