WCAG 1.4.10
Reflow
30%
of the 609 sites we scanned fail this
Ranging from 23.4% of US local government to 37% of US healthcare providers. Pooled across five targeted cohorts, so treat it as a convenience sample rather than a rate for the web.
What it means and how to fix it
What 1.4.10 covers
- We detect this: Content requiring horizontal scrolling at a 320px viewportFlagged for human confirmation rather than decided automatically, because the criterion permits exceptions and one of them may apply.
- We detect this: Content that genuinely needs two dimensions (data tables, maps, diagrams, toolbars)Excluded automatically. These are the exceptions the criterion itself allows, so flagging them would be a false positive.
- No engine can detect this: Content that reflows but becomes unusable, with overlapping or unreachable elementsNothing scrolls sideways, so the check passes. Whether the result is usable is a visual judgement.
Of that, one failure is detectable automatically, and these are what the rates on this page measure. Each needs its own fix. The percentage is the share of all 609 scanned sites affected. These do not sum to the 30% above: a site can fail more than one of them, and most that fail any fail several.
- Content forces side-to-side scrolling when zoomed30%
Users who zoom to 400% or view on small screens must scroll horizontally to read content, forcing a disorienting two-dimensional reading pattern.
What it looks like in code
CSS.layout {
width: 1200px; /* below a 1200px viewport this forces sideways scrolling */
}.layout {
width: 100%;
max-width: 1200px;
}A fixed width is the usual cause. The fix is almost always to cap the width rather than set it. Data tables, maps and diagrams are exempt from this criterion, so they do not need to be squeezed into 320px.
Shown for Content forces side-to-side scrolling when zoomed. Both halves are written rather than harvested: this failure lives in CSS rather than in the markup, so there is no page element to show.
For what the criterion formally requires, read the W3C Understanding document.
How often it fails
Share of scanned sites in each cohort. These are five targeted studies, not a random sample of the web, so read the contrast between cohorts rather than any one figure as a web-wide rate.
Who fails it most3 cuts by state, sector, retail vertical
By state
By sector
By retail vertical
Groups smaller than 8 sites are not shown: a rate over a handful of sites moves by tens of points on a single result.
What the numbers do not say
Banks are the outlier, and in the right direction: 1 of 19 EU banking sites requires horizontal scrolling at 320px, against 7 of 12 retail marketplaces. Responsive layout is old, solved engineering, and the sectors that invested in mobile web early are visibly ahead. It is one of the few criteria in this corpus where a regulated sector outperforms retail.
What this does not measureLimits of these figures, and where the corpus came from
- Some of these figures come from detectors that flag candidates rather than confirmed failures (reflow-horizontal-scroll-320), because the patterns they look for have legitimate exceptions. Treat them as an upper bound on confirmed failures.
- These are five targeted cohorts, not a random sample of the web. Per-cohort rates are the figure to quote; the pooled rate is a convenience sample.
- Denominators count sites that produced a result. Sites that were blocked or errored are excluded rather than counted as passing.
- Occurrence counts are floors: the engine records at most 25 occurrences of a rule per page.
- The EU and Indian cohorts retained only the primary success criterion per finding, so a rule mapping to several criteria contributes to one of them in those two cohorts and to all of them in the other three.
| Cohort | Scanned | Attempted |
|---|---|---|
| Shopify DTC stores | 75 | 75 |
| US local government | 158 | 221 |
| US healthcare providers | 208 | 218 |
| EU e-commerce | 107 | 170 |
| Indian financial services | 61 | 72 |
Corpus generated 2026-09-18.
Check your own site
A free scan reports WCAG 1.4.10 alongside everything else, with the exact elements that fail.
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