Definition: A screen magnifier is software that enlarges part of the screen, often many times over. Partially sighted people using one only ever see a small portion of the page, and move that view around with the mouse, the keyboard or the focus [1].
German: Bildschirmlupe · Also: magnification software · Last reviewed: 27 September 2026
How people work with magnification
Every major operating system includes a magnifier: Windows Magnifier, Zoom on macOS and iOS, Magnification on Android. Specialist programs add colour filters, smoothed fonts and speech. Some people only zoom in the browser with Ctrl + Plus – that is where reflow comes in. A magnifier, by contrast, enlarges the whole screen, and the page never knows.
That changes how a page is perceived. When you only see a slice, you cannot take in relationships at a glance. You have to go looking for them.
What goes wrong
- Messages at the far end of the screen: a "Saved" note at the top right while you type at the bottom left is never seen.
- Labels far from their fields: with the label on the left and the field on the far right, both will not fit in the view.
- Content that appears only on hover and vanishes as soon as you move the mouse to read it (WCAG 1.4.13).
- Focus that cannot be seen or hides behind a sticky bar: the magnifier follows focus, but if you cannot see it you lose your place (WCAG 2.4.11).
- Text in images, which pixelates when enlarged.
- Weak contrast, which stands out even more under strong magnification.
What your website needs
- Related things kept close together: label and field, error message and field, question and answer options.
- Status messages close to the action that triggers them.
- A clear focus indicator and enough contrast.
- Real text instead of images of text.
- Tooltips you can move the mouse onto without them disappearing, and that close with Escape.
How Reviseberg handles it
Reviseberg measures contrast with axe-core, and its keyboard agent checks whether focus is visible (keyboard:focus-visible) and whether it lands on something with no size or off-screen (keyboard:focus-invisible). Whether content stays together under strong magnification is not something Reviseberg tests. A zoom agent is not part of Reviseberg today; criteria such as 1.4.13 stay "untested" until a person records a result.
Related terms
Reflow · Contrast ratio · Focus indicator · Text spacing · Assistive technology