MKV vs AVI: Features, File Size, and Compatibility Compared

MKV (Matroska) is a modern container that supports virtually any codec, multiple audio tracks, embedded subtitles, and chapter markers. AVI (Audio Video Interleave) is a legacy Microsoft container from 1992 that works on almost any device but lacks modern features. For storing media collections, MKV is better. For maximum compatibility with older hardware, AVI still works.

Container Features

MKV can hold unlimited audio, video, and subtitle tracks in a single file. You can pack a movie with the original English audio, a Spanish dub, commentary track, and SRT/ASS subtitles all in one file. It supports chapters, tags, and attachments (like cover art or fonts). AVI supports one video track and one audio track. No subtitle support, no chapters, no metadata beyond basic tags. If you need subtitles with AVI, you use a separate .srt file alongside it.

Codec Support

MKV works with every modern codec: H.264, H.265, AV1, VP9, AAC, Opus, FLAC, and more. AVI was designed for older codecs like DivX, XviD, and uncompressed PCM audio. You can technically force H.264 into an AVI container, but many players will choke on it because AVI was not built for variable bitrate streams or B-frames.

File Size

The container format itself adds minimal overhead, so file size depends almost entirely on the codecs used. An H.264 video in MKV and the same H.264 video in AVI will be nearly identical in size. The practical difference is that MKV lets you use more efficient codecs (H.265, AV1) that produce much smaller files at the same quality. AVI users are typically stuck with older, less efficient codecs.

Compatibility

AVI plays on nearly every device made in the last 30 years: Windows Media Player, old DVD players, car head units, and cheap media sticks. MKV requires a player like VLC, MPC-HC, or a modern smart TV. Most streaming devices (Roku, Fire Stick, Chromecast) handle MKV fine, but some older TVs and basic media players reject it. Web browsers do not natively support either format; for web playback, MP4 is the standard.

When to Use Each

Use MKV for media archiving, personal libraries, and any situation where you want multiple audio or subtitle tracks in one file. Use AVI only if you have legacy hardware that requires it. For sharing videos or uploading to the web, convert to MP4 instead of using either format. If you have AVI files you want to modernize, converting to MP4 preserves compatibility while gaining modern codec support.

Need to convert video formats? Our video to MP4 converter handles AVI, MKV, and other formats. For more comparisons, check AVI vs MP4 and MOV vs AVI.