SWF is a format designed to store vector graphics and animation, it may contain sound, video, text and other data. Such files are widely used for creating animation, games and playing video and audio on web pages. It is possible to open SWF files with Adobe Flash Player or with a browser that has the flash plugin installed.

ASF is a media container used by Microsoft Windows Media Player. It was designed for streaming audio and video files online. The container determines the structure of the data stream but not how the data should be encoded. Usually the files encoded by Microsoft developers have the .wma or .wmv extensions, other files have .asf extension. Such files generally have MIME type that allows sending files via the internet. The main feature of the ASF is the ability to stream playback, that is the ability to play a video or audio directly at the time of downloading data over the network.