Default accessibility support set

[alastc]

From the WCAG3 explainer:

The concept of "accessibility-supported" is to account for the variety of user-agents and scenarios. How does an author know that a particular technique for meeting a guideline will work in practice with user-agents that are used by real people?

The intent is for the responsibility of testing with user-agents to vary depending on the level of conformance.

At the foundational level of conformance assumptions can be made by authors that methods and techniques provided by WCAG 3.0 work.
...
An "accessibility support set" is used at higher levels of conformance to define which user-agents and assistive technologies you test with. ...

So at the foundational level of conformance the methods / techniques we provide should be reasonably reliable.

That means we need an "accessibility support set" for foundational level requirements/methods/techniques/tests. Even though we might not call it that in the spec, if authors rely on our techniques, we need to know that they are supported by a reasonable range of assistive technology.

This is status-quo (the same as) WCAG 2, except that in WCAG 2 the baseline set of technology support wasn't explicitly defined, and there was no mechanism to define your own set.

In order for people/organizations/regions to define their own set, we need to define what they are varying from (the default set).

We should consider that:

• The larger the default set is, the more work it is to test methods/techniques. With too large a set, we might not be able to provide as wide a range of techniques.
• Including technologies which don't have good support for modern web techniques could restrict what we include at the foundational level.

Question

The question for this discussion is: What should our default "accessibility support set" be?

As an example, in the UK the Government Digital Service maintains a page which outlines which AT to test with for UK Gov orgs. They have defined their set.

That set is UK based, although the stats are partly from the US. Does anyone have publicly available versions of this type of information? It would be especially useful if it is from another region.

As a simple draft to generate discussion, and acknowledging my western & English-speaking bias, what if we used the most popular paid-for and free versions of each major type of AT?

• Speech input: I assume that would be Dragon/Win and Android speech intput?
• Magnification: Zoomtext and Windows Mag.
• Screenreader: Jaws and Voiceover/iOS

I'd like to include some AT for cognitive/learning disabilities, but they seem to be spread thin, it's hard to work out what would be considered popular. (Please correct this if you know of anything that would make a good default.)