Overlay vendors promise a one-line script will make a site compliant. The demand letters keep arriving anyway. Here is the gap between the marketing claim and what an automated check actually sees.
An accessibility overlay is a third-party JavaScript widget — accessiBe, UserWay, and similar — that injects a toolbar and a set of runtime "fixes" into a page. The pitch is simple: paste one line of script, become ADA compliant, stop worrying about lawsuits. The reality is that overlays change what a sighted user sees in a settings panel far more than they change what an assistive-technology user or an automated rule engine actually encounters.
The claim versus the page
Most sites that install an overlay also publish an accessibility statement — language like "this site meets WCAG 2.1 AA" or "fully keyboard accessible." That statement is a public claim. A plaintiff's firm reads it, then tests the page. If the page fails on the rules the statement names, the gap between claim and reality is the case.
Overlays frequently leave the underlying DOM violations in place — missing form labels, low-contrast text, focus traps — while adding a widget that asserts compliance. The statement says one thing; an axe-core scan of the live page says another.
What an automated check actually sees
OverlayRiskWitness loads the page twice in a real browser: once with the overlay running, once with it blocked. Both passes run the same automated WCAG checks. Rules that still fail with the overlay on are the ones that matter — the overlay had its chance to "fix" them and did not.
- Overlay on, rule still fails → the marketing claim did not hold up on this page.
- Overlay off vs on, no change → the overlay had no effect on that rule.
- Rule unreachable → the check couldn't evaluate it; that is a gap in evidence, not a pass.
Evidence, not a legal conclusion
None of this is a legal conclusion. OverlayRiskWitness documents observations with a timestamp and a snapshot hash, quotes the site's own statement back, and places the two side by side. Whether that gap matters legally is a question for counsel — but you cannot answer it without the evidence in hand first.