Video tool · Free

Compress MKV Online - Free

Shrink an MKV file without it falling apart. It comes back as a small MP4 that plays everywhere.

Free to start
In your browser
Up to 1GB

How it works

Compress MKV in 3 steps

Upload your MKV
Drag and drop the MKV file, or click to browse. Anything under 1GB.
A balanced level is pre-set
Compression and resolution start at a level most people cannot tell from the original. Push either further in the panel if you need it smaller.
Compress and download
The smaller file downloads as MP4. Create a free account to download it, or keep editing in REQO.

Why MKV files are big, and what comes back

MKV (Matroska) is an open container that can hold any codec plus unlimited audio tracks, subtitle tracks and chapters. That flexibility makes it great for archives and useless for sharing.

Browsers, phones and social uploads reject MKV almost universally.

Editing tools often refuse to import it, or import picture without audio.

The compressed file comes back as MP4 (H.264 video, AAC audio), not MKV. That is where most of the saving comes from: H.264 in MP4 is the most efficient format that every phone, browser and upload form accepts. If something downstream insists on MKV, convert the result back with the MP4 to MKV converter.

Container

Your MKVMatroska

The MP4 you get backMPEG-4 Part 14

Typical codecs

Your MKVAlmost anything: H.264, HEVC, AV1, VP9

The MP4 you get backH.264 video, AAC audio

Plays on

Your MKVVLC and desktop players; rarely anywhere else

The MP4 you get backEvery phone, browser, TV and editor

File size

Your MKVDepends entirely on the codec inside

The MP4 you get backSmall for the quality

Feature	Your MKV	The MP4 you get back
Container	Matroska	MPEG-4 Part 14
Typical codecs	Almost anything: H.264, HEVC, AV1, VP9	H.264 video, AAC audio
Plays on	VLC and desktop players; rarely anywhere else	Every phone, browser, TV and editor
File size	Depends entirely on the codec inside	Small for the quality

Before you compress an MKV

An MKV often holds several audio languages and subtitle tracks. Converting renders one video and one audio track, so extra languages and embedded subtitles are not carried over; add captions in the editor instead.

Browsers, iPhones and most upload forms do not accept MKV, which is why a file that plays in VLC still needs converting before it can be shared.

FAQ

compress mkv: questions

Will my MKV stay an MKV?

No, it comes back as MP4. The compressor renders H.264 video with AAC audio, which is both smaller than most MKV files and playable everywhere. Use the MP4 to MKV converter afterwards if you need the original container.

Does compression ruin the quality?

At the pre-set level most viewers will not see a difference. Quality only falls apart when you compress hard AND keep a high resolution, which is why the panel pairs a level with a resolution.

Is compressing MKV free?

Yes. Compress and preview free, and a free account downloads the result. Free exports and share pages include a small REQO badge. Go Pro to remove it.

Same tool, other presets