FLV is the flash video file format, which is widely used for delivering video content over the Internet. The video codec of FLV uses simplified variants of H.263 standard, commonly refereed to as FLV1 and FLV4. FLV has now been widely adopted by major video portals including YouTube, and MySpace. The easiest way to play FLV files is using VLC. You can also install and configure the FFDShow filter to enable your media player to play FLV files.