.swf File — Shockwave Flash

SWF (Shockwave Flash, or Small Web Format) is the file format for Adobe Flash content — interactive animations, games, applications, and video players that powered much of the interactive web from the late 1990s through the mid-2010s. SWF files contain vector graphics, bitmap images, audio, video, ActionScript code (Flash's programming language), and timeline-based animations in a compact binary format optimized for streaming delivery. Flash technology enabled the first generation of browser-based games (Newgrounds, Kongregate), interactive advertisements, rich internet applications, video players (early YouTube), and animated content that HTML/CSS/JavaScript couldn't achieve at the time. SWF files were executed by the Flash Player browser plugin, which was installed on over 99% of internet-connected desktops at its peak. Apple's 2010 exclusion of Flash from iOS, growing security vulnerabilities, and the maturation of HTML5 capabilities led to Flash's decline. Adobe officially discontinued Flash Player on December 31, 2020. The Ruffle project provides an open-source Flash emulator in WebAssembly for preserving Flash content. Internet Archive hosts thousands of preserved Flash games and animations.