Software program that magnifies all or part of a computer screen to make the content visible to users with visual impairments.

a device (or software) that will make images and text on a screen larger for the benefit of visually impaired users

A screen magnifier is software that interfaces with a computer's graphical output to present enlarged screen content. It is a type of assistive technology suitable for visually-impaired people with some functional vision; visually-impaired people with no functional vision usually use a screen reader.