FLV (Flash Video) is a container file format used to deliver video content over the internet using Adobe Flash Player or Adobe AIR. It was widely popular for streaming video on websites like YouTube before the adoption of HTML5 video. FLV files can contain video data encoded with codecs such as Sorenson Spark, VP6, or H.264, and audio data encoded with codecs such as MP3 or AAC. The format supports metadata, which can include information about the video, such as title, author, and creation date. While FLV is still supported by some older systems and software, it has largely been superseded by more modern video formats like MP4 due to its limitations and the decline of Flash Player. FLV files are often used for archived video content or in legacy systems that have not been updated to support newer formats. The format is designed for efficient streaming and playback, making it suitable for online video distribution, although it is less commonly used today.