F4V

F4V is a multimedia container format used for Flash Video content. It was developed by Adobe Systems and introduced with the Flash Player 9 era to carry video streams alongside audio for streaming and progressive download. The format is designed to work with the H.264 video and AAC audio codecs and is based on the ISO Base Media File Format (ISOBMF), the same underlying structure used by MP4. Files typically use the .f4v extension.

As a variant of ISOBMF, F4V uses the same box-and-atom layout as MP4, including tracks for video and audio, headers, and metadata. It is optimized for Flash Player and Flash Media Server delivery over HTTP or RTMP, enabling efficient streaming and synchronized playback. F4V generally supports progressive download and streaming, with a design that favors fast start times when moov data is readily accessible.

Compatibility and usage have shifted with the decline of Flash. While F4V can still be encountered in older archives and some specialized pipelines, MP4 with H.264/AAC has become the more common container for HTML5 video. Many multimedia tools and workflows can read or convert F4V files, and encoding or transcoding to and from F4V is supported by popular software such as Adobe Media Encoder and FFmpeg in various versions and configurations.

In practice, F4V served as the bridge between Flash-era delivery and modern video formats. Its relevance has diminished as HTML5 video and universal MP4 delivery have become standard, though it remains a part of the historical landscape of web video formats. See also FLV, MP4, H.264, AAC, and ISOBMF.