Flash requires a proprietary media-playing plugin to be seen. According to a study,^[3] 98% of US Web users have the Flash Player installed.^[4] The percentage has remained fairly constant over the years; for example, a study conducted by NPD Research in 2002 showed that 97.8% of US Web users had the Flash player installed. Numbers vary depending on the detection scheme and research demographics.^[5]

The most recent incarnation of Flash's scripting language (called "ActionScript", which is an ECMA language similar to JavaScript) incorporates long-awaited usability features, such as respecting the browser's font size and allowing blind users to use screen readers. Actionscript 2.0 is an Object-Oriented language, allowing the use of CSS, XML, and the design of class-based web applications.