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Video formats explained: MP4, MOV, MKV, WebM and AVI

Published October 13, 2026 · 3 min read

For sharing a video widely, MP4 with H.264 video and AAC audio is a practical starting point. MOV is common in Apple workflows, MKV is useful for multiple tracks, WebM targets the web, and AVI often belongs to older systems.

The extension does not determine picture quality. Two MP4 files can differ greatly in size and playback support because their codecs and encoding settings are different.

Container versus codec

A container organizes video, sound and other data. A codec represents and usually compresses each track. MP4, MOV, MKV, WebM and AVI are containers; H.264, HEVC, VP9 and AV1 are video codecs. ¹

Asking whether an app supports MP4 is only half the question. It also needs to support the codecs inside that MP4. An error might concern the picture, the soundtrack or a particular recording feature.

Compare the five formats

MP4 for everyday delivery

MP4 is widely used for distribution. H.264 with AAC is a conservative combination for phones and computers, although an MP4 can also contain HEVC or AV1.

If playback fails, inspect the codec before repeatedly converting the same file with settings that do not address the problem.

MOV in Apple workflows

MOV is the QuickTime file format. ² It can carry codecs chosen for capture, editing or playback. A MOV is not automatically sharper than an MP4.

The iPhone video on Windows guide explains why changing the container can preserve the original picture while leaving an HEVC playback problem unresolved.

MKV for several tracks

Matroska supports selectable video, audio and subtitle streams, along with chapters and metadata. ³ That makes it useful for keeping language versions together.

Check what a converter will retain. Imagyc, for example, writes only the main video and audio tracks: subtitles, chapters and extra tracks are left out. If those features matter, review the entire converted file rather than just a short playback sample.

WebM for the web

WebM was designed for web media and is based on Matroska, with a focused selection of codecs such as VP9 and Opus. ⁴ For a website, consider the browsers and devices your audience actually uses.

A smaller download that demands more decoding work is not automatically the best experience everywhere. Test playback and provide a compatible alternative when needed.

AVI for older material

AVI is Microsoft's RIFF-based container. ⁵ You may encounter it in archives, older equipment and legacy applications. It is not a codec and does not necessarily mean uncompressed video.

Imagyc currently does not read AVI files. Use an app that can decode the source AVI first, then export a copy in a supported format.

Choose and convert a video

1. Identify the destination: messaging app, website, editor or personal archive.
2. Check the containers and codecs it accepts.
3. Keep the original recording.
4. Open the video converter for supported files on your device.
5. Choose an output format and change quality or resolution only when needed.
6. Test sound, picture, orientation and any required tracks.

Imagyc works locally without uploading the file. Compatible tracks may be copied into a new container without re-encoding. Read the video compression guide for size reduction and the codec guide for the encoding choices.

Frequently asked questions

Which video format has the best quality?

There is no winner based on the extension. Source quality and encoding determine the result.

Is MKV always larger than MP4?

No. With the same encoded tracks, the size difference may be small. Additional tracks can increase the file size.

Will MP4 conversion remove every subtitle?

It depends on the converter. Subtitles burned into the picture remain visible; separate subtitle tracks need explicit handling.

Can I convert by renaming the file?

No. A new extension does not reorganize the file or change its codecs.