Reference

MKV

MKV (Matroska) is an open, flexible video container that can hold an unlimited number of video, audio, subtitle, and chapter tracks in one file. It is common for movies and downloads but is not natively supported by iOS, so it often needs converting to MP4.

Files & formatsGeneral

MKV

Also known as: Matroska, .mkv, mkv file, Matroska Video

Open Matroska container; holds many tracks in one file
Common for movies; not natively supported on iOS
Often converted to MP4 for phone playback

What makes MKV different

Like MP4 and MOV, MKV is a container — it wraps the actual video, which is compressed by a separate codec. What sets MKV apart is flexibility: a single .mkv file can bundle multiple audio languages, several subtitle tracks, and chapter markers.

That flexibility is why MKV is popular for full-length movies and TV rips. The trade-off is compatibility: MKV does not play natively in the iOS Photos app, Safari, or QuickTime without conversion or a third-party player.

MKV and storage

MKV files tend to be large, but that reflects what they contain — long, high-resolution video plus extra tracks — not the container itself. Re-wrapping an MKV as MP4 changes compatibility, not size, unless you also re-encode with a more efficient codec.

If MKV downloads are filling your device, the simplest fix is to keep only what you are currently watching and store the rest in the cloud or on external storage.

Related terms

Keep reading the reference.

Files & formatsContainer formatA container format is the file wrapper that packages compressed video, audio, subtitles, and metadata into one file — for example MP4, MOV, or MKV. It defines how the parts are stored together, not how they are compressed; the codec inside does that.General Files & formatsMP4MP4 (MPEG-4 Part 14) is the most common video container format. The .mp4 file holds video, audio, and subtitle streams together, but does not itself define quality — the codec inside (usually H.264 or HEVC) decides how large and how compressed the video is.General Files & formatsCodecA codec is the method used to compress and decompress video or audio — it decides how much detail is kept and how small the file becomes. Common video codecs are H.264 and HEVC (H.265); common audio codecs are AAC and MP3. The codec, not the file extension, controls quality and size.General Files & formatsMOVMOV is Apple’s QuickTime video container, the default format iPhones and Macs record in. Like MP4 it wraps video and audio streams rather than defining quality, and on Apple devices it typically holds HEVC or H.264 video.iOSmacOSGeneral

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