A buyer reviewing a responsive website should test a complete enlarged journey, not only a narrow screenshot. Agree how text, navigation, enquiry controls and necessary two-dimensional data behave when the effective viewport becomes small.
Primary evidence and claim boundaries
WCAG reflow guidance uses an equivalent 320 CSS-pixel width for vertically scrolling content, with exceptions for content requiring two-dimensional layout. Primary reference · Read 17 October 2026.
Filled acceptance example
Synthetic teaching scenario, not a client case, provider integration test or business result. Scroll the example table on narrow screens.
| Synthetic test condition | Task | Expected observation |
|---|---|---|
| 1280 CSS-pixel viewport at 400% zoom | Read service description | Equivalent width about 320 CSSpx; no lost text |
| Same enlarged context | Open navigation and find enquiry | Controls reachable; no overlay trapping content |
| Necessary data table | Read a long row | Local table scrolling; surrounding prose reflows |
| Validation message appears | Correct field and resubmit | Error and correction control remain visible/reachable |
Practical handover procedure
- Choose representative content with a long heading, navigation, a form error and dense data. Define the actual browser, viewport and zoom; device pixels are not CSS pixels.
- Walk the whole task using the enlarged view and keyboard. Separate unavoidable two-dimensional components from ordinary text; a wide page wrapper is not a blanket exception.
- Capture failing states and the resulting data/feedback, then repeat after changes to fonts, banners or sticky controls. Keep zoom and mobile-width tests as complementary evidence.
Interpret the outcome
A page can fit 390 pixels and still fail when a zoomed menu hides its final link. Conversely, a necessary table may scroll locally without justifying horizontal scrolling for every paragraph. The acceptance unit is the completed reader task with no information lost.
Acceptance decision
Record whether every task step remains operable and all essential content remains available. A viewport calculation is a setup aid, not a conformance result.
Limits and unverified work
Teaching test matrix, not an audit of the frozen homepage or a full WCAG assessment. Actual browser zoom can differ due to browser chrome and device settings; record the effective viewport.
Download the filled bilingual acceptance record — Contains these inputs, steps, expectations and limits. This is a teaching record, not an executable integration.