1Upload every file you want combined — at least two of them.
2Drag the uploaded items into the order you want; the order is taken from the list, not from the filenames.
3Start the merge, which joins matching inputs without re-encoding them and reconciles mismatched ones exactly once.
4Download the single combined MKV file.
Merge MKV FAQ
Is the merge lossless?
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It is whenever the inputs already agree — the encoded data is copied straight through. It stops being lossless only when the inputs disagree and something has to be re-encoded to make them compatible, and even then it is one pass, not one per file.
Can I control the order things are joined in?
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Yes — drag the uploaded items into the order you want before starting. Order is taken from the list, not from the filenames, so "IMG_2.jpg" sorting after "IMG_10.jpg" is not a problem you have to solve first.
Does it matter if the inputs are different formats?
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It does. MKV imposes no codec restrictions and carries unlimited audio, subtitle and chapter tracks, which is why rips use it and TVs often refuse it. Matching inputs take a fast, lossless path; mismatched ones have to be reconciled to a common format, which is slower and costs one encode.
Anything specific to MKV when merging?
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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. That is worth checking when the inputs did not all come from the same source.
Will Merge 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 Merge 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 Merge MKV cost anything?
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No. Merge 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.
Why does a WebM site host Merge MKV?
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WEBM.to is built around the container the open web actually chose — VP9 or AV1 with Opus audio, decoded natively by every modern browser and needing no plugin, licence or player. Video is the case where extra round trips hurt most — the files are large and every upload costs real minutes. Running Merge MKV on the same pipeline as the conversions means one upload covers the whole job instead of one upload per tool.
What should I do with the result once Merge MKV is finished?
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The converter on this site moves video between WebM, MP4, MKV, MOV and the rest, or pulls the soundtrack out entirely, without another upload. Sequencing it that way matters more for video than anywhere else: each re-encode is another generation, so the fewer of them stand between the source and the file you publish, the better it looks.
Is Merge MKV here the same tool the sibling sites run?
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The engines are shared — the same ffmpeg build with x264, x265 and libvpx, the same workers, the same limits. What a WebM site adds is a view on containers and codecs: which combinations play everywhere, which need a re-encode and which can simply be copied across. It also starts from one fact about the format this site is named after: WebM is VP9 or AV1 with Opus audio, which browsers decode natively but which most desktop editors still transcode on import.
Do I need an account, and does anything get kept?
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No account, and nothing is kept: uploaded video is deleted from the workers shortly after the job finishes, nothing is watched and nothing is indexed. Free accounts exist for history and batch size, not for access.
