Windowless Mode

Windowless mode is a legacy Adobe Flash rendering option (wmode=transparent or wmode=opaque) in which the Flash player drew into the browser's graphics surface directly rather than into its own dedicated OS window. It was commonly used so that HTML content could overlap Flash content, or to allow transparent backgrounds. The accessibility consequence was severe: in windowless mode, Flash content did not expose itself via Microsoft Active Accessibility (MSAA), so screen readers could not see the buttons, text, or controls inside the Flash at all. Any page using wmode=transparent was, for practical purposes, entirely invisible to assistive technology. Although Flash itself is obsolete, windowless mode remains a useful case study in how rendering choices made for visual effect can silently destroy accessibility.