MKV Compressor
Compress MKV videos online. The result stays an MKV, with H.264, H.265 or AV1 video and AAC sound.
Compress an MKV file and keep it an MKV
This MKV compressor re-encodes the video of your MKV at a lower bitrate and returns a smaller file that is still an MKV, so players and media servers that read MKV still take it. Upload one MKV up to 1 GB; it is compressed on our server and deleted 30 minutes after the result is ready.
You choose the codec, the Quality and the Resolution. You can compress 10 videos a day for free, with no account, and the limit is shared with the other video compressor pages.
Which codec to pick for an MKV
The Codec menu offers three. The Quality slider sets the target bitrate the same way for all of them, so the codec changes how much detail fits and where the file plays, not the size:
| Codec | Result at the same Quality position | Encoding time | Plays on |
|---|---|---|---|
| H.264 Default | Baseline detail | Fastest | Almost every player, TV and phone |
| H.265 | More detail at about the same size | Slower | Recent devices; some older ones fail |
| AV1 | Most detail at about the same size | Slowest | Newer players only |
Because H.265 and AV1 keep more detail at the same bitrate, you can lower Quality further with them for a similar look. A source that is already H.265 or AV1 often shrinks little, because the work a better codec does has been done. What each codec is and how bitrate fits in are explained in what is a codec and video bitrate, explained.
The three settings that reduce MKV file size
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Quality
Lower values give a smaller file with more visible compression, because the target bitrate scales with the slider. Drag it down a step at a time and compare.
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Resolution
Keep original, or pick a lower height such as 1080p or 720p. Only heights lower than your video are offered, so a video is never upscaled.
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Convert HDR to SDR
For an HDR source, this converts the colours to standard range, which suits screens and players that show HDR washed out.
When compression is not what you need
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Situation
Every audio and subtitle track must stay exactly as it is.
Better choiceCompression re-encodes the sound to AAC at 192 kbps and does not promise to keep every track. To keep tracks untouched, change the container without re-encoding, as in convert MKV to MP4 without re-encoding.
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Situation
You need an MP4 or another format, not a smaller MKV.
Better choiceUse the video converter to turn an MKV into MP4, MOV or WebM.
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Situation
You have videos in other formats too.
Better choiceThe video compressor takes MP4, MOV, WebM and more, and has pages for MP4 and MOV.
Compression is lossy: the result is never identical to the original, so keep the source file until you have watched the new one.
How to reduce MKV file size
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Drop the MKV
Add one MKV file up to 1 GB. The panel shows its codec, bitrate, length and resolution.
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Choose codec, quality and resolution
Keep H.264 for the widest playback, or pick H.265 or AV1 to keep more detail at about the same size. Lower Quality or Resolution for a smaller file.
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Compress and download
Click Compress MKV and download the result within 30 minutes, before it is deleted.
MKV compressor questions
You can't remove size without some loss, because compressing re-encodes the video. Keep Quality high and Resolution on Keep original for the least visible difference, or try H.265, which keeps more detail at the same Quality position.
Yes. The result is an MKV with H.264, H.265 or AV1 video and AAC sound.
Not guaranteed. The sound is re-encoded to AAC at 192 kbps, so if every track must stay untouched, remux the file instead of compressing it.
A video already in H.265 or AV1 has little left to remove. Lower the Quality slider or the resolution, or keep the original.
Both keep more detail than H.264 at about the same file size, so you can lower Quality further for the same look. They take longer to encode and play on fewer older devices, and AV1 keeps the most detail and is the slowest.
Yes: 10 videos a day, up to 1 GB each, with no account. The result is deleted 30 minutes after it is ready.