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Re: Detection of adaptive technology

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From: Benjamin Hawkes-Lewis
Date: Oct 10, 2008 2:10AM

Mackenzie, Hamish wrote:
> I was just chatting with a colleague about the analytics package we are
> using for our web site and we thought it would be a great stat if we
> had some idea of the numbers of visitors to our site that are using AT
> such as screen readers. I am sure I have visited some web sites that
> were aware I was running a screen reader, not that I can think of an
> example right now, and I was just wondering if any of you had any
> experience of whether this is possible or not.

On Windows systems with Flash installed and enabled you can detect the
use of Flash's Microsoft Active Accessibility (MSAA) interface:

http://osflash.org/flashaid

Users of MSAA include many Windows AT, including screen readers such as
JAWS, Window-Eyes, HAL, screen magnifiers such as ZoomText, and speech
recognition like Dragon Naturally Speaking. But the users also includes
automation software, such as is employed for testing software, so there
could be false positives. There would also be false negatives as not all
Windows assistive technology uses MSAA, for example the Fire Vox
self-voicing extension for Firefox, Opera Voice, the Hawking Toolbar for
Firefox, and on-screen keyboards. Equally importantly, there would be a
large category of unknowns including:

* Windows AT users with Flash disabled (a substantial contingent, given
the accessibility problems presented by typical Flash content).

* AT users not using Windows (e.g. GNOME Orca and Apple VoiceOver or
MacSpeech Dictate users).

The sites you visited that appeared to be aware you were running a
screen reader might have been using this technique. Or, they might have
been styling content directed at screen reader users off-screen with CSS
or putting it into the ALT attribute of a pixel GIF, so that mostly only
screen reader users would consume it.

--
Benjamin Hawkes-Lewis