Add your MKV file
Drop one or more .mkv files onto the converter above, or browse for them. They load into browser memory only — nothing is uploaded, so there is no size-based pricing and no server queue.
MKV to WEBM
Converting .mkv video to .webm means re-encoding the picture and sound into a different container and codec family, and this page does it entirely in your browser. Free, private, and validated — the file never leaves your browser.
Private for supported formats — processed in your browser
Runs on your deviceConvert supported files
Drop MKV files here
Batch files can each use a different output. Nothing uploads for local conversions.
Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.About converting Matroska video to WebM video
Converting .mkv video to .webm means re-encoding the picture and sound into a different container and codec family, and this page does it entirely in your browser. An .mkv file uses the Matroska container, an open format designed to hold an unlimited number of video, audio, and subtitle tracks in one file. Collectors of high-quality rips and archival copies favor .mkv because it keeps every language track, chapter marker, and font attachment together.
A .webm file is an open, royalty-free video container built specifically for the web. It restricts itself to free codecs, VP8, VP9, or AV1 for video with Vorbis or Opus for audio, so any browser can play a .webm without patent licensing concerns. For this route the practical draw is free of patent royalties end to end and vP9 and AV1 deliver excellent compression efficiency — balanced against older iPhones and legacy Safari versions cannot play it, which is worth knowing before you commit a large batch.
Why convert MKV to WEBM?
The practical trigger for this conversion is usually a mismatch: with .mkv, safari and iOS refuse the container outright. Switching to .webm buys you free of patent royalties end to end, which is why it is the better fit for serving HTML5 video without codec license fees. Because the conversion runs locally, trying it costs nothing but a few seconds of compute on your own machine.
MKV vs WEBM at a glance
| Aspect | Matroska video (.mkv) | WebM video (.webm) |
|---|---|---|
| Format type | Container — quality depends on the codecs and settings inside | Container — quality depends on the codecs and settings inside |
| How it stores data | built on EBML, a binary XML-like structure that lets the container gain features without breaking older parsers | structured as a deliberately restricted subset of Matroska's EBML layout |
| Strongest at | archiving discs while preserving every audio track and subtitle stream | serving HTML5 video without codec license fees |
| Weak spot | safari and iOS refuse the container outright | older iPhones and legacy Safari versions cannot play it |
| Metadata | matroska tags cover title, cast, and arbitrary key-value pairs, and the container can embed cover art and other files as attachments | only a minimal set of Matroska tags such as title and language is defined for WebM; the spec deliberately omits attachments and rich tagging |
Pick WEBM as the output
Select .webm in the output menu next to each file. The menu only offers targets this engine can genuinely produce, so if WEBM is selectable, the route is real and validated.
Convert on your device
Press Convert. The conversion runs on an FFmpeg engine compiled to WebAssembly, executing entirely inside your browser tab.
Verify and download
Each result is signature-checked before the download unlocks, so a failed encode can never masquerade as a valid WEBM file. Outputs keep the original filename with the .webm extension.
MKV to WEBM questions, answered
Will converting MKV to WEBM lose quality?
Both sides are re-encoded, so expect a small generation loss controlled by the quality setting: mkv is container-oriented and webm is container-oriented. For visually or audibly transparent results keep quality high; for smaller files lower it and compare.
Is it private to convert MKV files here?
Yes — the .mkv file is processed inside your browser tab and never uploaded. The conversion runs on an FFmpeg engine compiled to WebAssembly, executing entirely inside your browser tab. Close the tab and the file is gone from memory.
Where will the WEBM file work?
Chrome, Firefox, and Edge have played WebM for over a decade, and Safari added playback in 2021 starting with version 14.1 on macOS, with iOS following in iOS 15. Beyond browsers the picture thins out quickly, since many televisions, set-top boxes, and editors still expect MP4.
Will the WEBM file be bigger or smaller than my MKV?
It depends on the content: structured as a deliberately restricted subset of Matroska's EBML layout. Convert one representative file first and compare before batch-processing a large set.
What happens to the metadata in my MKV file?
This converter strips container metadata deliberately (the FFmpeg command runs with metadata mapping disabled) so exported files do not leak recording details. In the source, matroska tags cover title, cast, and arbitrary key-value pairs, and the container can embed cover art and other files as attachments; none of it is transmitted anywhere because the file never leaves your browser.
Can I convert WEBM back to MKV?
Yes — the reverse route exists as a separate tool. Bear in mind that round-tripping .mkv → .webm → .mkv is not a perfect undo when any lossy step is involved; keep your original if fidelity matters.