A screen magnifier enlarges part of the screen, from the zoom built into every operating system up to dedicated software like ZoomText. That one runs from 1x to 60x, with fractional steps such as 1.4x at the bottom of the range, and down there a user still sees most of the page. Push the magnification up and the view narrows to a small moving window, so two things far apart on screen are never seen together. A confirmation drawn on the opposite side of the page from the button just clicked may as well not have rendered. Magnification is not browser zoom. Magnifying the screen enlarges what is already drawn and leaves the viewport alone, so the page does not reflow to fit, which means the reflow rule that rescues a zoom user does nothing in that mode. The rules about where things sit relative to each other still do a great deal.
In practice
At high magnification in the ordinary pixel-magnifying mode you read through a keyhole, and what that costs is relationships rather than detail. An error message at the top of a form and the field it refers to at the bottom may never be seen at the same time. Magnification solves a problem of sharpness by creating a problem of field of view. That is why somebody with normal peripheral vision running a magnifier hits the same difficulties as somebody with peripheral field loss.
It is not the same adaptation as browser zoom, and the site rule that rescues one does not rescue the other. Browser zoom shrinks the viewport, which is what makes a page reflow to fit. Magnifying the screen enlarges whatever is already drawn and leaves the viewport untouched, so nothing reflows and the content stays exactly as far apart as it was, only bigger. That is the magnification mode rather than the whole product. ZoomText's own reading views can reformat and wrap text, so ask which mode somebody was in before you conclude their tool never reflows anything.
Bigger is not what everybody wants, either. Somebody with good sharpness and tunnel vision may reduce the text size so more words fit inside the field they have. That is the most counter-intuitive thing in the whole subject, and it means one user's setting can be another user's barrier. Let the browser do its job rather than picking a size on somebody's behalf.
ZoomText is a product line, not a product. There is a magnifier, a magnifier with a screen reader in it, and a third product pairing the magnifier with JAWS. Somebody telling you they use ZoomText may be using speech as well, and its text rendering means high magnification is not necessarily the blurry mess people picture.
We looked for a measurement of how many people use magnifiers and did not find one. Screen reader surveys catch only the products that also read aloud, and a magnifier-only user has no reason to answer one. That looks like a gap in the field's evidence rather than in our research, and the honest answer to "how many" is that we have not found a number worth quoting.
Why it matters
It explains why placement is a real design decision rather than a detail. Nothing in WCAG says an error has to appear beside its field or take focus, and the status message rule deliberately allows a message to be announced without focus moving at all. What magnification changes is the cost of getting placement wrong, because at that size distance across the page is the same as being on another screen. It also explains the rule about content that appears on hover or focus. W3C's own worked failure is a magnifier user hovering something, getting a pop-up larger than their view, scrolling to read it, and watching it vanish because scrolling took the pointer off the trigger.
The window problem
At four times magnification, four times in each direction, a user sees about a sixteenth of the screen area at once. A confirmation drawn in the opposite corner may as well not have rendered.
Where this shows up on the site
Related terms
- Low visionLow vision is sight loss that ordinary glasses cannot correct, and it covers far more ground than a single blurred-vision picture suggests.
- ZoomZoom means enlarging a page, usually with Ctrl or Cmd and the plus key, and two WCAG rules govern what has to survive it.
- ReflowReflow is content rearranging itself to fit a narrow viewport instead of making you scroll sideways to read every line.
- Assistive technologyAssistive technology is hardware or software that gives a person with a disability more than a mainstream browser offers on its own.
- High contrast modeHigh contrast mode is an operating-system setting that throws away most of a site's colours and paints the page in a palette the user chose.
Knowing the word is the easy part.
Find out where your own site stands. The free scan checks 10 pages in a real browser against all 90 supported automated rules, separates 27 best-practice checks from its WCAG findings, and names the rule behind every result.