Each of the Screen Readers we've come across seem to do things their way, and have differing levels of support for:
- different accessibility features;
- browsers; and
- operating systems
We need to determine which screen reader(s) we intend to make Moodle work best with in order to choose the most optimal solution for these readers.
Our selection also has a big impact upon the amount of time it requires to develop new functionality and changes, and to test it.
From the compatibility matrix I've created so far (http://goo.gl/b4cVb5), there are approximately 30 combinations of screen reader + browser + operating system available to users.
Ideally, this should be as few combinations as possible because as we add each combination, the complexity increases dramatically, as does the time required for development and testing.
The ideal solution would be for a single, well documented, well tested, and widely available screenreader, but as http://goo.gl/b4cVb5 shows, this will not be possible as no screen reader supports both Windows, Macintosh, and Linux whilst providing support for multiple browsers.
Whilst Mobile support would be desirable, I think initially we should focus on improving the support for desktop screen readers as a priority and look at adding mobile combinations later.
Data suggests that the most widely used primary Reader by far is Jaws  though it's usage has seen rapid decline over the past few years.
Jaws is followed in popularity by Windows-Eyes, and Apple's Voiceover.
ChromeVox is the only screen reader we've come across to support the same browser across multiple operating systems which may also be an important consideration for some users. At present its market share is low (0.2% ) but it is new to the arena - from what I can tell it was only released in February 2012  with the survey taking place in May 2012.
NVDA, which came in at fourth place in the webaim survey is also an interesting option as it is the highest ranked free solution for Windows, though it is only compatible with Windows and the Firefox + IE browsers.
To offer the most widespread selection it makes sense to choose from the following subset of screen readers.
I have not, at this stage, commented on the ease of development for each screen reader at present, or it's comparative support for various accessiblity functionality.
- High market penetration
- Cost to users
- Windows only
- Internet Explorer only
- Mid-level market penetration
- Windows only
- Firefox and Internet Explorer only
- Supports all browsers tested
- Also available on iOS
- Mac OS Only
- Cross-Operating system
- Google Chrome only