SWF is the file format used by Macromedia Flash to deliver graphics, animation and sound over the Internet. Not really an "image" format. This, of the 4 formats for this assignment, is the only 'vector' based format. It is primarily used for animation and interactive content; however it can be used to deliver vector graphics to websites, so long as the user has the required plug-ins, and almost 95% of web users can view SWF content without having to install a new plug-in. Images saved in the SWF formats tend to retain there color and resolutions even when when they are zoomed in or zoomed out.