A container is the wrapper format that packages encoded video, audio, subtitles, and timing/metadata into files - distinct from the codec, which is how the media inside is compressed. The container defines how a player finds and synchronizes the tracks.
Streaming has largely converged on fragmented MP4 (fMP4), the basis of CMAF, replacing the older MPEG-TS used by legacy HLS. fMP4 lets the same segments serve both HLS and DASH, which halves storage and CDN cache footprint. Choosing one container/segment format across protocols is a key simplification in modern packaging.
