I'm a graduate student studying computer science at the University of Washington. One of my research interests is web accessibility, so after the university changed its homepage to have a large Macromedia Flash component, I found myself wondering how accessible such content was for the wide variety of students at the university. I have to admit that initially I didn't know what to think of this change. I knew that it was possible to provide alternatives for Flash content (having done so myself years ago when the question was whether or not a user would have the Flash plugin installed) but I didn't know how adequate such alternatives were. In this article I hope to answer the question of whether the University of Washington's choice was a good one and, generally, whether Flash is always a bad move when it comes to accessibility.
To start my research I talked to a Flash developer I know* and looked online for relevant resources. In short, Flash by itself is at best moderately accessible on Windows, using IE and a recent (<=2-4 year-old) version of Flash. I'm not convinced that all use of Flash is bad, but there's no reason for the Flash on the homepage of the University of Washington and, worse, they aren't keeping their alternative content up to date.
In the mid 90's dialup ruled the Internet and Flash was conceived of as a way to put animations on the web while retaining a small file size. It uses vector graphics that are small and can be easily scaled without sacrificing quality (this is actually an accessibility advantage for people with low-vision). The company didn't fully anticipate the effect of allowing user interaction in Flash animations until after releasing version 4.0 when they revamped the product and added more support for handling user interaction. Subsequent versions (5.0, available in ~2002 and later versions) have had increasing levels of accessibility support. The most recent version (8.0) achieves some level of accessibility by communicating through IE to screen readers. Because other browsers don't implement the standard that Microsoft established, other browsers cannot pass on the accessibility information on to screen reader applications.
It's always been possible to provide alternatives to Flash, although originally it was mainly intended as an alternative for users that didn't have the Flash plugin installed. As usual, the onus is on the web designer to provide accessible alternatives to Flash and, for a number of reasons, I suspect that web authors are even less likely to take the time to provide good alternatives, partly because they may be less capable of providing good alternatives for some Flash content.
As an example illustrating alternative content, consider an old website of mine, not updated since ~1999: http://www.solscape.com/ It's easy to detect if Flash is turned off in the browser and put in text/image map equivalents. "Equivalent" is a loaded word, but alt text is a text equivalent for image content and it's generally seen as acceptable in that context. For Flash that acts as a menu or text, it's easy to determine what an equivalent alternative would be, but for videos or interactive animations/games it may not be as easy.
The menu to the left on my page referenced above is Flash and is not accessible because it was developed with the version of Flash available at the time which did not have accessibility features. If Flash is turned off, however, the page displays an accessible imagemap instead. I argue this isn't unreasonable. In general, non-Flash content will be more accessible so why have Flash turned on? One potential problem is that Flash is included with and switched on by default in both Firefox and Internet Explorer. Web designers may best maximize accessibility when using Flash by writing accessible Flash and only displaying the Flash content when the user is using Internet Explorer and the detected version of Flash is capable of using the accessibility features employed. Both of these can be reliably detected using Javascript - if the user does not have Javascript enabled then alternative content should be displayed.
The important questions for the web designer is whether the Flash content adds value to the webpage that offsets its potential accessibility barriers and whether such value be added in other ways? I think for most pages that employ Flash, alternative HTML/AJAX/CSS methods of handling content would achieve the intended effect without sacrificing accessibilty, but this isn't always true.
In some cases, the line is blurrier. In the webpage that I offered as an example above, the menu didn't need to have the fancy animated background, but as long as I provide an alternative, on the same page, with the same content, that the user has to do nothing additional to view, I don't see the harm. Because the amount of content contained in both is small, it is also likely that the two versions would stay in sync. In other cases when the Flash content includes useful video or animated images to increase understanding I think it would be unreasonble to look down on a website for providing it.
But, back to the the question at hand. Should the University of Washington's homepage include Flash? The answer is a firm and obvious no. Their use of Flash is completely without added value - it potentially causes accessibility problems and accomplishes nothing that couldn't be achieved with regular HTML, CSS and Javascript. Their non-flash version proves that point. Furthermore, at the time of this writing (5/2/06) the flash version includes content about the upcoming Windemere Cup and this content is not reflected in the non-flash version, illustrating the common problem with separate but equivalent content - the content for the audience in the minority is lower priority and updated less frequently. Finally, the Flash version of the website is inaccessible even by a user using Internet Explorer and a sufficiently recent version of Flash. The Flash content includes many links, but these links are impossible to reach via the keyboard. Furthermore, the submenus are not accessible via the keyboard and their content is not replicated by traversing the associated menu items.
If done correctly, Flash can be accessible, but the University of Washington fails miserably at achieving accessibility on its homepage.
* Michael Bond has been a Flash developer for years. Check out his website, keepfrozen.com, for great stuff, including his Flash portfolio.