SWF File Format

File Format Description

SWF is currently the dominant format for displaying animated vector graphics on the web which is very popular and be commonly used. What's more, SWF is sometimes used for creating animated display graphics and menus for DVD movies, and television commercials.

Files using the SWF extension are media files that require the Adobe Flash plug-in to render. SWF files are used for a variety of applications -- from video embedding to entire websites -- and can create dynamic, visually rich media to create an interactive environment. These files are usually embedded, or included, when websites load, and most users will never need to download them separately.

Causes of Failed Playback

Generally speaking, to play SWF movies, you need to install Adobe Flash Player to your computer, or install Flash player plug-in to your Web browsers. However, there's no Adobe Flash Player or Flash plug-in available for Mac users. Besides, neither iOS nor Android supports Flash any more. Therefore, if you are playing SWF on Mac or iOS/Android devices, you probably will fail. To solve this problem, you have to convert SWF to other popular video formats like MP4 beforehand.
Referrence: How to Convert SWF to MP4