Visual testing
Test Page Reflow at 400 Percent Zoom
Published by whatisADA / Grow Wild Agency · Updated
Purpose and preparation
Check a vertically scrolling page at a width equivalent to 320 CSS pixels. A common desktop setup is a 1280 CSS-pixel-wide viewport enlarged to 400 percent. Record the effective viewport instead of assuming a device's physical pixel width is equivalent.
A practical example
A service directory changes from several columns to one, while its filter controls and result descriptions remain available without horizontal page scrolling.
How to check it
- Set and record the initial viewport, then zoom to produce an effective width of 320 CSS pixels. Inspect the main reading flow without reducing the zoom.
- Open navigation, filters, validation messages and sticky panels. Look for content that overlaps, vanishes or requires scrolling in two directions to read ordinary paragraphs.
- Review any claimed exception, such as a data table or map, separately. Check whether surrounding headings and controls still reflow and document why two-dimensional layout is necessary.
What can be missed
The exception for content needing a two-dimensional layout does not exempt the whole page. A wide table should not force every paragraph to scroll horizontally.
Record your test
Use this worksheet to record what you actually checked. Notes stay on this device when you choose Save; they are not sent to us. Avoid personal or confidential information on shared devices.
These are your observations, not automated results or a conformance certificate. A complete evaluation needs appropriate scope, supported technologies, all applicable criteria and relevant page states.
Primary sources and scope
This is independent implementation guidance with original examples. The linked standard contains the full definitions, exceptions and conformance requirements. A criterion or checklist alone does not establish legal applicability or whole-site conformance.