Touch screen acting on its own: charger, screen protector or panel?

Apps opening by themselves, a keyboard typing random letters: these are called "ghost touches". The screen isn't always the cause. Test in this order.

1. The charger

A poor-quality charger or cable creates electrical interference that the screen reads as touches. Unplug the phone: if the ghost touches stop, change the charger.

2. The screen protector

A cracked or badly fitted glass protector (air bubble, raised edge) can press on the panel all the time. Remove it to test.

3. Moisture and dirt

Clean the screen with a slightly damp cloth, then a dry one, and dry your hands.

4. Software

Restart the phone and install system updates. A buggy app can also cause strange behaviour: try safe mode (Android).

5. The touch panel

Open the touch screen test and slide your finger over the whole grid. If an area never changes colour, or if cells light up without you touching the screen, the panel is damaged. This is common after a drop, even without a visible crack. Only replacing the screen will fix it.

Tell us your phone model in a reply, and whether the screen has been replaced before.