Android
Turn Auto-Rotate On or Off auf Android
Auto-rotate reads data from the accelerometer and orientation sensor to decide how content is displayed. When the setting is off, the screen stays locked in the orientation it was in when you disabled it, no matter how you hold the phone. When it is on but the screen still does not react, a stuck sensor, a case blocking the sensor area, or an app that forces its own orientation can all be the cause.
You control this behavior under Settings ➔ Display ➔ Auto-rotate screen. Toggling it on lets the display follow the physical position of the device; toggling it off keeps the current orientation permanently, which is useful for reading in bed or watching a fixed layout without accidental flips.
If rotation still fails after enabling the option, check whether the quick settings panel has its own rotation lock icon active, since that toggle can override the menu setting. Some apps, especially camera or media players, also lock their own orientation regardless of the system setting, which is normal and not a bug.