Step 1: Supply your WebM files using the button above or by haul and lay.
Step 2: Click the 'Convert' button to start the conversion.
Step 3: Get your converted MKV files.
WebM to MKV Conversion FAQ
Will resolution and frame rate be preserved in the MKV?
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Yes. WEBM → MKV keeps resolution, frame rate, and aspect ratio unchanged by default. To change them, use the Resize or Speed tool on the result.
Is the WEBM to MKV conversion reversible?
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You can convert the MKV back to WEBM on this site. If either format involved is lossy, the round-trip is not bit-perfect even though it is visually or audibly close.
Can WEBM be converted to MKV without re-encoding the video?
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No, not on this page. WEBM and MKV share the same underlying structure, but the converter re-encodes the video for this pair rather than copying the stream, so it takes longer than a container change and the picture is compressed again. Choose High Quality under Quality to keep the most detail. WebM is a strict subset of Matroska that Google published in 2010 specifically to give HTML5 video a royalty-free container. MKV is Matroska, an open container designed in 2002 with no licensing restrictions and no ceiling on what it can hold.
Why do so many people keep their libraries in MKV?
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Because it was designed for keeping things rather than for delivering them. An MKV holds an unlimited number of audio tracks, selectable subtitle streams, chapter marks and cover art in one file, which is exactly what a disc rip needs somewhere to put — everything ends up in a single object instead of a folder of loose companions. The trade is playback: very little consumer hardware decodes it natively, so the same file that is ideal on a computer or a media server usually has to be converted again before a television will touch it. MKV is the archival container of choice because it stores unlimited audio tracks, soft subtitles, chapter markers and cover art in one file.
Can the MKV hold more than one audio track?
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Yes, and it is a real upgrade over WEBM. MKV treats every audio stream as a first-class track, so an original-language mix, a dub and a director commentary can live in one file with the player switching between them on demand.
Does MKV support chapter markers that WEBM did not?
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It does. MKV stores chapters as container metadata, so a long recording can be navigated by section instead of by scrubbing a progress bar. WEBM has nowhere to put that information, so the converted MKV starts with no chapters; add markers afterwards with a tool such as MKVToolNix or ffmpeg.
Can I still embed the file on a web page after converting WEBM to MKV?
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Not directly. WEBM plays inline in every browser; MKV does not, so a page embedding it falls back to a download link or an empty player frame. If the file is destined for a website, keep the WEBM for the web and treat the MKV as the archive or editing copy. MKV has almost no native hardware support — phones, browsers and TVs usually need VLC or a remux before they will play it.
Will the MKV still play smoothly on a phone or a TV?
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It may not. WEBM is decoded by dedicated silicon on phones, tablets and TVs, which is why it plays without flattening the battery. MKV typically falls back to software decoding on the same hardware — higher CPU load, a warmer device, and dropped frames on 4K material. For a device target, WEBM is the safer container to stay in.
Is there a file-size limit when converting WEBM to MKV?
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Free conversions have a size limit per file, set by the type of file, and the page tells you when a file is over it. A paid plan removes that limit, so much larger files can be converted.
Can I batch-convert several WEBM files to MKV at once?
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Several files in one job need a paid plan. Free use is one file per conversion, one conversion an hour. On a paid plan you can add several files to one job, then download each result on its own or all of them in one ZIP.
What happens to my WEBM files after the conversion?
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Uploaded files are processed on our own conversion servers, nobody looks at them, and they are not shared. The upload and the converted file are both deleted automatically about 24 hours after the conversion, which leaves time to download the result. See /privacy/ for the full policy.
Will my MKV play on phones, tablets, and TVs?
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Yes — MKV uses modern codecs that play natively on iOS, Android, Smart TVs, game consoles, and every modern browser.
