What an overlay cannot do, in one page
When our scanner finds an accessibility overlay on a site, the report says which vendor, and then says plainly what the product does and does not fix. That is a finding, not a sales opportunity, so it sits with the other findings.
The short version
An overlay is JavaScript that runs after your page loads. It can restyle things. It cannot know that an image is a diagram of your pricing, or that a field wants a billing address rather than a delivery address. Meaning is not in the page for a script to find.
In January 2025 the Federal Trade Commission brought an action against accessiBe over its claims about exactly this. Litigation trackers have reported for years that many of the sites sued had an overlay installed at the time.
The longer version, with sources, is in our guide on overlays.