Once known as Macromedia Flash, Flash is a multimedia player and software system used for games, animation, rich Internet applications (RIA) and the creation of vector graphics. Flash is commonly used to embed video or audio streaming players, interactive media and advertising into web pages.

The related Adobe Flash Player renders Flash content playable across various desktop computer systems and devices, and is available as a free plug-in for common web browsers and select smart-phones, tablets and other mobile devices.

Flash files are rendered in the SWF format, often referred to as ShockWave Flash, Flash applications or Flash movies, which generally end in the .swf file extension. Flash video files use the .flv extension, and are employed either within .swf files, or played back through a player like QuickTime or Windows Media Player that has been rendered flv-compatible by adding an external codec.

In November of 2011, Adobe announced that it would no longer support Flash for mobile platforms or television systems, opting to focus on HTML5 to deliver browser-based content and Adobe AIR to serve mobile app stores. Despite its difficulties in the mobile environment, the Flash Player is still required for viewing a great deal of website content, often making such websites incompatible with mobile devices.