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
What does the WEBM to MKV converter do?
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It transcodes a WEBM video into the MKV container. Resolution, frame rate, and aspect ratio are preserved by default — useful when you need a different format for a target player without quality loss.
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.
Will the converted MKV be a different size than the WEBM?
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Modern codecs compress better, so MKV from a legacy WEBM is typically 30-60% smaller at equivalent quality. Conversions in the opposite direction can grow the file.
Can WEBM be converted to MKV without re-encoding the video?
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Yes, and it is the fast path. WEBM and MKV share the same underlying box structure, so the video and audio streams are copied across byte-for-byte and only the container wrapper is rewritten. Nothing is decoded and nothing is re-compressed, so a feature-length file finishes in under a minute instead of half an hour, with output quality identical to the source. 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 if the source shipped with a chapter list it was in a sidecar file — hand that to the converter and it gets written into the MKV.
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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Anonymous uploads are capped at a generous default; signed-in free accounts get a higher cap, and Pro accounts have no per-file limit. Browser memory is usually the practical constraint long before our server-side limits kick in.
Can I batch-convert several WEBM files to MKV at once?
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Yes. Drop or pick multiple WEBM files in one upload — the converter processes them in parallel and returns a ZIP of the MKV results. There is no need to repeat the upload step per file.
