PreBoard

PreBoard, like SpringBoard, is a core app from Apple that is included with iOS and iPadOS, but is normally concealed from general user access.

Functionality
PreBoard initially displays the Apple logo at boot, but is a bit brghter until it fades into the Passcode Lock Screen. It also has 4 more screens. If you reboot your iPad, iPhone, or iPod Touch while an installation in an update, PreBoard will launch and say “press home to upgrade” with a white background, and ask for your password, if you have one, then send you to the default Update interface. If you update via iTunes, DFU, or migrate filesystems (from HFS+ to APFS) on an iOS device, it will be the same white screen, but it says press home to recover instead of press home to update. It also asks for your passcode twice. After, it takes you to a screen similar to the update screen, but it is white (no matter what color the device is) and the bottom says “Attempting data recovery”. When this screen is left for a few seconds, it sleeps without fading. There is also a “preparing” variant without the text. If data recovery fails, it says “Data recovery could not be completed. Please restore iPhone from backup.” PreBoard was first included with iOS 8. , and the data recovery feature was added in iOS 12.

"When PreBoard is launched at an abnormal time, it presents a white screen and a prompt: “Press home to upgrade” (“Swipe to upgrade” on devices with no home button). This is a very indirect way of asking for authentication. When you open PreBoard and authenticate, it shows you the Apple logo (as if you were booting your device) for a second, and then it takes you to the home screen. If a shortcut was running, it continues running."