The Safe area is that portion of the whole video frame considered safe for important information. Typically it occupies the centre 90% of the screen, giving a 5% border on all edges.
Domestic television sets overscan – that is, they display the pictures slightly too large to fit on the visible screen. This is done to hide imperfections in the television set’s handling of sharp changes in brightness (which cause the picture to bow and distort). This overscan is not fixed and can vary widely; particularly on older television sets. Typically around 5% of the image is lost on each edge.
Professional television monitors and computer displays do not use overscanning and the concept of a safe area does not apply.