A screen reader is a software application which, rather than presenting web content visually, converts text into 'synthesised speech' allowing user to alternatively listen to content. In more accurate terms – content displayed in screen is sent to standard output, whether a video monitor is present or not. Interpretations are then synthesised to the user with text-to-speech, sound icons, or a Braille output device. Screen readers are a form of assistive technology (AT) which are essential to people who are blind, as well as useful to people who are either visually impaired, illiterate or suffer a learning disability.