En Accessibility overlays are not for disabled people:
An accessibility overlay (or accessibility widget) is one of those wee icon-only buttons you sometimes see floating over a web page; usually in the bottom-right corner. When you press them, they give you a bunch of options to make the website ‘more accessible’.
Why did I use inverted commas? Well, they profess to make a website more accessible, but do little-to-nothing of any real use; in fact, they can actually hinder a disabled user’s experience of a website!
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Accessibility overlays are for non-disabled people by non-disabled people. The only way to properly address accessibility issues is at the product development level: carefully considered designs and well written code. Adding a single line of JavaScript to your website or app is not the answer.