MP4 is the universal video container — the .mp4 file extension that practically every video on every device speaks. Whether it's a TikTok download, a YouTube upload, a Slack attachment, an iPhone recording, a Netflix download for offline viewing — almost certainly an MP4 file. Standardised by ISO/IEC in 2003 and built on Apple's earlier QuickTime format, MP4 became universal because it does one thing well: hold compressed video plus audio plus metadata in a way every player understands.
A common confusion worth clearing up: MP4 doesn't define how the video inside is compressed. The compression is done by a codec (H.264, HEVC, AV1, etc.) and MP4 is just the wrapper around the result. So an .mp4 file might contain H.264 video (the safe universal default), HEVC video (modern, more efficient), or AV1 video (newest, even more efficient) — same .mp4 extension, very different bandwidth requirements and device compatibility. When a viewer says "this MP4 won't play", the problem is almost never the container; it's the codec inside.
In 2026, MP4's biggest practical variant is fragmented MP4 (fMP4), used for HLS and DASH streaming. The standard MP4 format is for downloads, social posts, attachments, archival — anywhere the whole file lives as one piece. Together, regular MP4 and fragmented MP4 cover essentially every video delivery scenario on the modern internet. If you're starting a new project and don't have a specific reason for something else, ship MP4.
