Why it matters

Container choice affects compatibility and features. Understanding matters for delivery decisions.

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The architecture

MP4 (ISO Base Media): most compatible. Supports H.264, H.265, AV1, AAC audio.

MKV (Matroska): highly flexible. Supports any codec, many streams, chapters, subtitles.

Common containersMP4universal compatMKVflexible, featuresWebMweb + Google/MozillaStreaming often uses fragmented MP4 (fMP4) for HLS and DASH
Container comparison.
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How it works end to end

WebM: subset of MKV. VP8/VP9/AV1 video, Vorbis/Opus audio. Designed for web.

fMP4: fragmented MP4. Standard for HLS + DASH streaming.

MOV (QuickTime): older Apple container, similar to MP4.

Remuxing: repackaging same streams into different container. Fast; no re-encode.