Video container format used by Adobe Flash; based on the ISO MP4 format, which is based on the Apple QuickTime container format; specified by ISO/IEC 14496-12 as a base media file format; supported by Flash Player Update 3 (9,0,115,0) and higher.

F4V files are similar to .FLV files, but use "boxes" to store data. Examples of boxes supported by the F4V format are the ftyp box (player requirements), the moov box (file header), the mvhd box (playback information), the trak box (media tracks), the uda box (free-form user data), the meta box (metadata), and several others.