MP4 vs MOV vs MKV - Which Container When

Last reviewed 2026-04-27. Use the video converter for in-browser format changes without uploading the file.

What "container" means vs "codec"

The container holds the video stream, audio stream, subtitle tracks, and metadata in one file. The codecs inside encode the actual pixels and audio samples. A .mp4 file usually contains H.264 video and AAC audio; a .mov file usually does the same; a .mkv file might contain H.265 video, FLAC audio, and three subtitle tracks. The container decides what can be carried; the codec decides how it is encoded.

Most playback issues are codec issues, not container issues. A video that "won't play" probably has a codec the player does not support, even though the container is fine. A .mp4 with H.265 video will not play in older browsers; a .mp4 with H.264 plays everywhere.

The three containers side by side

Container	Plays in browser	Multi-track	Subtitles	Default codecs
MP4	Yes (with H.264)	Limited	Limited	H.264 / AAC
MOV	Mostly (Apple flavors better in Safari)	Yes	Yes	H.264 / AAC, ProRes for editing
MKV	No (browsers do not support)	Yes (many tracks)	Yes (multiple subs)	H.264, H.265, AV1, FLAC, Vorbis

When to pick each one

MP4. The default for any video going to a non-technical recipient or to the web. Embeds in HTML5 video, plays in every browser, plays on every phone, plays in every messaging app. The 95% case.

MOV. Right when the video is staying inside the Apple pipeline - shot on iPhone, edited in Final Cut, delivered to another Mac user. ProRes-encoded MOV is the standard for video editing because the codec is intra-frame (every frame stands alone, no inter-frame dependencies, fast scrubbing).

MKV. Right for archival of source material with multiple language tracks, multiple subtitle tracks, and chapter markers. Pirated movie scene releases use MKV almost exclusively because the container handles everything they need to ship. Wrong for sending to a non-technical recipient because most consumer apps cannot play MKV.

Converting between them

Container conversion is usually fast and lossless because the inner codecs do not need to be re-encoded. MOV-to-MP4 with the same H.264 codec inside takes seconds and produces an identical-quality file at almost the same size. MP4-to-MKV is similarly fast.

Codec conversion is slow and lossy - re-encoding from H.265 to H.264 means decoding every frame and re-encoding it, which takes minutes per minute of video. Avoid codec conversion unless the destination requires it.

The video converter handles common container changes in the browser. For deeper context see MP4 vs WebM for the web or ffmpeg online vs local ffmpeg. Video tools at the video tools hub.