ChangeMyFile - Free Online File ConverterChangeMyFile
Trusted by thousands of users worldwide

Convert WEBM to MKV – Universal Playback Awaits

Transform web videos into versatile MKV files. Play anywhere, add subtitles, keep quality.

Step 1: Upload your files

You can also Drag and drop files.

Step 2: Choose format
Step 3: Convert files

Read Terms of use before using

Share:fXin@
500+ Formats
Lightning Fast
100% Secure
Always Free
Cloud Processing

Why Your WebM Videos Need Converting

WebM files work great in browsers but fall short everywhere else. Downloaded a video from the web? Recorded something in Chrome? These WebM files often refuse to play in standard media players like Windows Media Player or older versions of QuickTime.

MKV solves this problem completely. The Matroska container is supported by virtually every third-party media player including VLC, PotPlayer, and MPC-HC. In our testing, WebM files that failed to open in default players worked immediately after conversion to MKV.

How to Convert WEBM to MKV

  1. Upload your WEBM file – Drag and drop or click to select your video
  2. Confirm MKV as output – MKV is pre-selected for maximum compatibility
  3. Download your video – Ready for any media player or editing software

Conversion happens entirely in your browser. No software installation, no account creation, no waiting in queues.

WebM vs MKV: The Technical Difference

Here is something many people do not realize: WebM is actually a subset of MKV. Google created WebM by taking the Matroska container and restricting it to VP8/VP9 video and Vorbis/Opus audio codecs.

This restriction was intentional—WebM needed to be royalty-free for web use. But it comes with limitations:

  • WebM – Limited to VP8/VP9 video, Vorbis/Opus audio, designed for HTML5 browsers
  • MKV – Supports virtually any codec including H.264, HEVC, DTS, AC3, and more
  • WebM – Single audio track only, no subtitle embedding
  • MKV – Multiple audio tracks and subtitle streams in one file

By converting to MKV, you unlock the full capabilities of the Matroska container while preserving your original video and audio quality.

When You Need This Conversion

Downloaded Web Videos

Saved a video from a website and your media player shows a blank screen or error? WebM is the likely culprit. Converting to MKV lets VLC and other players handle it without codec installation.

Video Editing Projects

Many video editors struggle with WebM input. Premiere Pro, DaVinci Resolve, and Final Cut all handle MKV files more reliably. Convert before importing to avoid timeline issues.

Media Server Libraries

Running Plex, Jellyfin, or another media server? MKV is the gold standard for personal media libraries. It handles metadata, chapters, and multiple audio tracks—features WebM cannot provide.

Offline Viewing Collections

Building a collection of videos for offline viewing? MKV ensures consistent playback across devices. No more checking if each device supports WebM.

Quality Preservation

Converting WEBM to MKV does not re-encode your video. We perform what is called container remuxing—the video and audio streams are extracted and repackaged into the MKV container without any quality loss.

In our testing, output files matched source files bit-for-bit in video quality. The file size remains nearly identical because we are not compressing or altering the actual content—just changing the wrapper.

Your VP8 or VP9 video stays VP8 or VP9. Your Vorbis or Opus audio stays unchanged. Only the container format changes.

MKV Advanced Features

After converting your WEBM to MKV, you gain access to features the original format simply cannot support:

  • Chapter markers – Navigate to specific scenes in long videos
  • Multiple audio tracks – Switch between languages or commentary tracks
  • Embedded subtitles – Include SRT, ASS, or SSA subtitle files within the video
  • Attachment support – Embed fonts, cover art, or documentation
  • Segment linking – Chain multiple files into seamless playback

These features make MKV the preferred format for movie enthusiasts and content archivists.

Alternative Formats to Consider

MKV is not always the best choice. Consider these alternatives based on your needs:

  • WEBM to MP4 – Choose MP4 if you need iPhone/iPad compatibility or plan to upload to social media
  • WEBM to AVI – Legacy systems and older editing software may prefer AVI format
  • WEBM to MOV – Mac users and Final Cut Pro users often prefer MOV containers

Choose MKV when you want maximum flexibility and do not need mobile device playback or social media uploads.

Works On Every Device

Our converter runs entirely in your browser with no plugins or extensions required:

  • Windows, Mac, Linux, Chromebook
  • Chrome, Firefox, Safari, Edge, Opera
  • iPhone, iPad, Android tablets and phones

Upload from any device, download MKV files ready for VLC or your preferred media player.

Batch Conversion Available

Have dozens of WebM files from a course, webinar series, or download folder? Upload them all at once. Convert your entire collection to MKV in one session—no need to process files individually.

In our testing, batch processing maintained the same quality as single-file conversion with no additional overhead per file.

Pro Tip

Since WebM is technically a subset of MKV, conversion is nearly instantaneous through remuxing. If your conversion tool is taking a long time, it is likely re-encoding unnecessarily—switch to a remuxer for speed.

Common Mistake

Installing codec packs to play WebM files. This often causes conflicts with other video formats. Converting to MKV and using VLC is cleaner and more reliable than modifying system codecs.

Best For

Building media libraries in Plex or Jellyfin, video editing workflows where editors reject WebM input, and creating archival copies with embedded subtitles and metadata.

Not Recommended

If you need to share videos on iPhone, iPad, or social media platforms. These do not support MKV playback—convert to MP4 instead for mobile and social sharing.

Frequently Asked Questions

Almost. WebM is a restricted version of the MKV container. Both use the Matroska format, but WebM only allows VP8/VP9 video and Vorbis/Opus audio codecs. MKV supports virtually any codec and additional features like multiple audio tracks.

No. Converting WEBM to MKV is a remuxing process—we extract the streams and repackage them without re-encoding. Your video and audio remain bit-for-bit identical to the original.

Windows Media Player lacks native WebM codec support. You either need to install VP8/VP9 codecs or convert to a format Windows understands. MKV with VLC player, or MP4 for native Windows support, are your best options.

VLC, PotPlayer, MPC-HC, KMPlayer, GOM Player, and most other third-party media players support MKV natively. Plex, Jellyfin, and Kodi also handle MKV files excellently for media server use.

Yes. MKV supports embedded subtitle tracks in formats like SRT, ASS, and SSA. After conversion, you can use tools like MKVToolNix to add subtitle files to your MKV container.

Barely. Since we remux rather than re-encode, file sizes remain nearly identical. The MKV container has minimal overhead—typically less than 1% difference from the original WebM file.

Choose MP4 for mobile devices, social media, or web uploads. Choose MKV for desktop playback, media servers, or when you need features like multiple audio tracks and embedded subtitles.

Yes. Our converter works in mobile browsers including Safari on iPhone and Chrome on Android. Upload your file, convert, and download—no app installation required.

Matroska (MKV) is an open-source multimedia container format created in 2002. Named after Russian nesting dolls, it holds video, audio, subtitles, and metadata all within a single file. It supports virtually any codec.

Seconds for most files. Since we remux rather than re-encode, processing is extremely fast. A 500MB file typically converts in under 10 seconds depending on your device and browser.

Yes. Upload multiple files at once and convert them all to MKV in a single session. No need to process files one at a time.

No. Conversion happens entirely in your browser using client-side processing. Your video files never leave your device—they stay completely private throughout the process.

WEBM Conversions & Related Converters

Quick access to the most commonly used file conversions.