HTML Versus Flash
Flash is a well-respected tool able to deliver interactive components to multiple browsers and platforms, but can be problematic for screen readers and mobility impaired users. Although Macromedia is committed to providing tools to develop accessible Flash tools, ensuring Flash accessibility can be difficult.
Tip: HTML Shell, Flash Objects
Although many developers create entire modules in Flash, including navigation functions, it may be easier to maintain the navigation, text and images in HTML and use Flash only for key animations, interactive activities or multimedia elements (audio/video).
When navigation is in HTML, options for accessibility are generally easier to implement.
In order to make Flash files more accessible, consider these recommendations:
Whenever possible, start animations and movies in pause mode, then allow the user to start and stop them as needed. Avoid endless loop animations, as they can be distracting for many users.
WCAG 2.0 Guideline 2.2—"Provide users enough time to read and use content."
Link to an XML caption file for Flash video whenever possible. See Flash documentation and tutorials for details.
Avoid including a full-screen automated Flash movie on a homepage, since mobility impaired users may not be able to exit, and cognitively disabled users may become disoriented. These Flash files should be started by the user.
Provide keyboard alternatives for common actions, and enable tabbing in forms. For example, you can both include a zoom button and program the "+" and "-" keys for zooming in and out. See Flash documentation and tutorials for details.
WCAG 2.0 Guideline 2.1.1—"All functionality of the content is operable through a keyboard interface without requiring specific timings for individual keystrokes, except where the underlying function requires input that depends on the path of the user's movement and not just the endpoints."
Add text labels to all controls, form fields, labels and components so they can be identified by a screen reader. See Flash documentations and tutorials for details.
WCAG 2.0 Guideline 3.3.2—"Labels or instructions are provided when content requires user input."
WCAG 2.0 Guideline 4.1.2—"For all user interface components (including but not limited to: form elements, links and components generated by scripts), the name and role can be programmatically determined."
Flash files should follow the same principles for font styling, color schemes, blinking objects, animations and audio and video accessibility that HTML pages do. One advantage of Flash files is that images and text are vector-based, and are therefore usually zoomable.
Keep text together in one object whenever possible. Screen readers may jump from text object to text object in unexpected directions.
NOTE: ActionScript can be used to control reading order in newer versions of Flash.
Minimize navigation within a Flash interface. This will minimize the amount of accessibility features needed within Flash.