Macromedia Flash, or simply Flash, refers to both a multimedia authoring program and the Macromedia Flash Player, written and distributed by Macromedia (recently targeted for acquisition by Adobe Systems), that utilizes vector and raster graphics, a native scripting language called ActionScript and bidirectional streaming of video and audio. Strictly speaking, Macromedia Flash is the authoring environment and Flash Player is the virtual machine application used to run the Flash files, but in colloquial language these have become mixed: "Flash" can mean either the authoring environment, the player or the application files.

The Flash files (or "Movies"), which usually have an SWF file extension, may appear in a web page for viewing in a web browser, or for "playing" in the standalone Flash Player. Flash files occur most often as animations, advertisements or design elements on web pages and, more recently, Rich Internet Applications. A Flash file can contain more diverse information than a GIF or JPEG file of the same size.