1Drop your MKV videos into the box above, or pick them from your device — there is nothing to install and no account to create.
2Choose how hard to squeeze: a quality or bitrate target, and optionally smaller dimensions if size matters more to you than detail.
3Start the job and let the workers re-pack the file; your original is never modified in place.
4Compare the new size against the original, then download the compressed MKV file.
Compress MKV FAQ
How does Compress MKV actually make the file smaller?
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Concretely, the picture is re-encoded through x264 or x265 at the CRF you set, optionally scaled down first; CRF 23 is visually transparent on most footage and each step of about six roughly halves the file again. Nothing about it depends on you installing software: the job runs server-side and hands back a finished file.
How much smaller will my file get?
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Almost entirely by the bitrate you choose and by how much the picture moves. A screen recording or a locked-off talking head compresses enormously, because most of each frame is identical to the one before it; handheld footage, grain, rain and confetti are the worst cases. Once the obvious wins are gone, lowering the resolution saves far more than lowering the quality further.
Does the format of my file change how much I can save?
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Very much so. MKV imposes no codec restrictions and carries unlimited audio, subtitle and chapter tracks, which is why rips use it and TVs often refuse it. That determines both the headroom available and whether the saving costs you anything in fidelity.
Is there anything specific to MKV I should know before compressing?
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Yes — MKV places no restriction on what is inside it, so an edit has to carry every audio, subtitle and chapter track across rather than assuming one of each. It is worth knowing before you overwrite an original you might need again.
What is the most common mistake when compressing MKV videos?
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Compressing the same file repeatedly. Each pass on a lossy format is a fresh generation of loss and the savings shrink while the damage accumulates. Go from the original to your target in one step, and keep the original.
What do I get back, and can I control the trade-off?
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A single compressed file per input, at a quality or bitrate level you choose rather than a fixed default. If the result is still too large, lowering the resolution or trimming the duration does far more than pushing the quality setting further down.
What can I upload to Compress MKV?
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MP4, MOV, MKV, WebM, AVI, WMV, FLV, 3GP, M4V, MPEG and MPG. The container and codec are probed before anything runs, so a mixed batch is handled correctly per file rather than assumed to be uniform.
Is there a file size limit on Compress MKV?
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Yes: free accounts process video up to 1 GiB per file, by far the most generous cap on the site; ffmpeg with x264, x265 and libvpx does the work, which is the same toolchain behind most desktop video software. Video is the one family where the cap is high enough that upload time, not the limit, is what you will actually notice.
Will Compress MKV lower the quality of my MKV videos?
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It depends on whether the job needs a re-encode. Operations that only touch the container or the timeline are done as a stream copy and the picture is bit-identical to the source. Anything that has to redraw frames goes through x264/x265 at a quality level you set, where CRF 23 is visually transparent on most footage.
Can I run Compress MKV on several MKV videos at once?
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Yes. Uploads queue in parallel, which matters more here than anywhere else because video jobs are minutes rather than seconds. Free accounts run one file at a time; a pass lifts that.
What happens to audio, subtitle and chapter tracks?
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They are carried across. Multi-track audio, embedded subtitle tracks and chapter markers survive wherever the target container can represent them — that is the main thing that separates a proper job from a naive re-encode that silently keeps only track one.
Does Compress MKV cost anything?
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No. Compress MKV is free without an account, and the output carries no watermark, no corner logo and no intro card. Uploaded video is deleted from the workers shortly after the job completes.
