Android
Factory Reset via Settings auf Android
A factory reset restores the phone to the state it was in when it left the factory. The Reset options menu under system settings triggers this process and wipes the internal storage completely.
Removed data includes the linked Google account, all app data and settings, installed apps, and locally stored media such as photos, music, and videos. Usage data tied to accounts and system logs is also erased. None of this can be recovered afterward, so a backup beforehand is essential if you want to keep anything.
To start the reset, go to Tap on Settings ➔ Tap on System ➔ Tap on Reset options ➔ Tap on Erase all data (factory reset) ➔ Tap on Erase all data. The phone reboots and shows the initial setup screen once the wipe finishes.
A factory reset makes sense when the phone runs slow across the board, before a resale or trade-in, or when persistent software glitches do not respond to smaller fixes. If only one app misbehaves, clearing that app's data or cache is usually enough and avoids losing everything else.
One side effect to plan for: after the reset, the phone may ask for the Google account that was active before the wipe. This is a security check, so make sure you remember those login details before you erase all data.