The Difference Between SWF & FLV
Both Flash Video format and Small Web Format media files are played through Adobe's Flash and AIR software; however, the former is intended for streaming video content and the latter is intended for animation content. FLV and SWF are referred to as Flash content. Both FLV and SWF are container files, which means neither ascribes to a specific media format; both containers have overlapping features. The limitations of each container type help define the use-case and differences between the two.
1 Adobe Flash Reads Both
Computers and other devices must have Adobe Flash or Adobe AIR installed to be able to play FLV and SWF content. According to Adobe, Flash Player is installed on 98 percent of Internet-enabled desktop computers and over 800 million mobile devices. Apple's iOS-running devices are not compatible with FLV and SWF content. Devices that are incompatible with Flash formats or don't have a compatible playback program installed can't display Flash-based website content and videos; many sites implement alternate content to work around Flash incompatibility.
2 FLV: Full Motion Video
FLV files are standalone Flash media content consisting of only full-motion video and related audio content. FLV files do not use any of the vector graphics or animation techniques found in SWF files. Unlike SWF files, FLV content does not enforce a maximum number of frames, allowing the content to be any duration. FLV containers can have video content in H.264, VP6, JPEG, PNG and GIF formats and support audio tracks in the MP3 and AAC formats. FLV video is often used for streaming content services like YouTube because the video can be progressively played back during the download process.
3 SWF: Shockwave Flash Animation Container
SWF is a container file that includes vector graphics, text, video and sound content intended for online use. While SWF has the capability of including full-motion video content, the container's graphic animations are intended to perform similar display effects on websites with a smaller file size. SWF also includes compatibility with the ActionScript programming language, which can be used to build interactive elements. Video elements can be included within SWF files, but are not the sole element within the container.
4 FLV Can Be Embedded in SWF
SWF supports all the features of FLV in a limited capacity, while FLV only supports SWF's video and audio playback elements. A complex SWF file may feature one or more embedded FLV elements. For example, a SWF advertisement may play a simple vector animation with static pictures on a website. If the user interacts with the SWF ad by clicking on it, the ad could do something like play back a FLV advertisement. The SWF file can also use ActionScript to impose interactive pause and mute buttons for the advertisement.