iPhone - Bottom Half of Screen Disappearing

For quite some time I experienced what I thought was a strange issue on my iPhone where the bottom half of the screen would suddenly disappear, or "scroll" down underneath the viewable area of the screen - just like in the picture below;

Original home screen

Home screen after "Reachabiliy" activated

 




















After a little bit of research, I found out that is actually a feature within the iPhone software known as "reachability". The idea being that the top half of the screen scrolls or moves towards the bottom of the screen, to make items that were originally at the top of screen more accessible when using the device with one hand. Pretty clever, right?

Reachability is activated by double tapping (note: not double pressing) the home button. Ie. tap the home button twice rapidly, but don't actually press the button down so it 'clicks'

Press the home button or tap anywhere on the screen to return the screen to normal