MKV to WebM Converter

What happens when you convert MKV to WebM

• The video is re-encoded to VP8 video with Vorbis audio.
• Re-encoding in a browser is slow: expect several times the video's length for HD footage on a laptop, and longer on a phone. Short and low-resolution clips finish much sooner.

How to convert MKV to WebM online

1. Press "Choose MKV files" and select one or more files, or drag them onto the box. You can add files of any size your device can hold in memory.
2. Adjust the settings if you need to: resolution and quality control the size of the result. The defaults suit most people.
3. Press "Convert to WebM". The first audio or video conversion downloads the converter engine, about 32 MB, which your browser then keeps for next time.
4. Save each WebM with its download button. Close the tab and every trace of the files is gone from memory.

Why convert MKV to WebM?

MKV files usually come from films and TV rips, OBS recordings and anime releases. People convert them to WebM because WebM is royalty free and plays natively in web browsers, which makes it a good fit for embedding video on a web page.

In short, MKV is good at what it was made for, and WebM is the more practical choice when the file has to play, upload or edit somewhere else. Chrome and Edge play many MKV files; Safari and iPhones do not, while WebM plays in Chrome, Firefox and Edge, and in Safari since version 14.1.

How to convert MKV to WebM on Windows, Mac, iPhone and Android

On Windows

Open this page in Chrome, Edge or Firefox, drag your MKV files in from File Explorer, and press Convert. Each WebM is saved to your Downloads folder. If you prefer a desktop program, VLC can also convert MKV to WebM: choose Media, then Convert / Save.

On a Mac

Safari, Chrome and Firefox all work. Drag the MKV files from Finder onto the drop zone and the WebM files land in Downloads.

On iPhone and iPad

Open the page in Safari and tap Choose MKV files. You can pick from Photos or from the Files app. The converted WebM appears in Files, in the Downloads folder; to put it in your photo library, open it there, tap Share and choose Save Video.

On Android

Open the page in Chrome, tap Choose MKV files and pick them from Files or your gallery. The WebM is saved to the Download folder, where any file manager can find it. Keep the screen on while a long video converts, because Android may pause a tab in the background.

Best settings for MKV to WebM

WebM is written as VP8 video with Vorbis audio. The Resolution setting is the one to reach for: 1080p keeps full HD detail, 720p is plenty for phones and laptops and roughly halves the size, and 480p suits email and old devices.

The quality levels map to the H.264 CRF scale where the target uses H.264, and to fixed high-quality settings for older codecs such as MPEG-2, MPEG-4 Part 2, WMV and Theora. Re-encoding always costs a little detail, so convert from the best copy of the MKV you have.

MKV vs WebM: the differences

About MKV and WebM files

What is an MKV file?

MKV can hold unlimited audio tracks, subtitle tracks and chapters in one file, which is why film rips use it. OBS offers MKV recording because a crash part way through does not corrupt the whole file.

What is a WebM file?

WebM is a royalty-free subset of Matroska made for the web. Browser screen recorders and many online meeting tools save to WebM, which iMovie and many editors cannot import.

MKV to WebM not working? Common problems

• The conversion is slow. Audio and container changes take seconds, but re-encoding video runs on your own processor. Lower the resolution to 720p, close other tabs, and keep the device plugged in.
• The tab stops or reloads on a very large file. Browsers limit how much memory one tab can use, around 2 GB and less on phones. Split long recordings or convert them on a computer.
• The WebM will not play on an old device. Try the other formats offered for MKV, or choose 720p, which older players handle more reliably.

Convert MKV to WebM with ffmpeg

This converter runs ffmpeg inside your browser. If you would rather use the ffmpeg command line on your own computer, this command produces an equivalent WebM with the same kind of settings:

ffmpeg -i input.mkv -c:v libvpx -b:v 1500k -c:a libvorbis -q:a 5 output.webm

Replace input.mkv with the name of your file. For a whole folder of MKV files, run the command in a loop, or drop them all on the converter above, which processes them one after another.