Convertior

Free Video Converter

Convert MP4 to MKV

Convert MP4 files to MKV online. The tool runs in your browser for supported files and the guide below explains when this conversion is useful.

Convertior free online media converter logo

Free Online Media Converter

Convert images, audio, video and documents for free directly in your browser.

Your files stay on your device. No upload required.

Unit Converter

Convert to

Browser conversion works best with smaller files. Large video files may require a modern browser and may be slower on mobile.

Convert files online for free

Convertior is a free online media converter for images, audio, video and documents. You can convert common file types such as JPG, PNG, WEBP, MP3, WAV, MP4, MOV, PDF, TXT, Markdown, HTML and JSON.

Private browser-based conversion

Files are processed locally in your browser whenever possible, which means they do not need to be uploaded to a server. This makes conversion simple, private and fast for smaller files.

Supported file conversions

  • Image converter: JPG, JPEG, PNG, WEBP, AVIF, BMP, GIF, TIFF, ICO, TGA, PPM, PGM and PBM
  • Audio converter: MP3, WAV, OGG, M4A, AAC, FLAC and OPUS
  • Video converter: MP4, MOV, WEBM, AVI, MKV, MPEG and GIF
  • Document converter: PDF, TXT, HTML, Markdown and JSON

Free MP4 to MKV converter

MP4 is optimized for compatibility and web sharing but is less flexible than MKV for complex media packaging.

MKV is a flexible container used for archiving, local playback and workflows that may need more track flexibility.

Best for

Creating an MKV version for local playback

Best for

Using a container favored by media-center software

Best for

Testing a file in apps that prefer MKV

How to convert MP4 to MKV

  1. Choose or drop your MP4 file in the converter.
  2. Select MKV as the output format.
  3. Adjust quality or bitrate settings if they appear for this file type.
  4. Click Convert Now and keep the tab open until the download is ready.

Quality and file-size notes

  • The visual quality depends on whether the video is re-encoded and what settings are used.
  • MKV can be useful as a container, but it does not improve source quality.
  • Keep the original MP4 when compatibility matters.

Limitations before you convert

  • Some browsers or devices do not play MKV natively.
  • Multiple tracks and subtitles may need specialist tools for advanced control.

File privacy

For supported conversions, Convertior processes files inside your browser. That design avoids unnecessary file uploads and is one reason the tool may feel faster for small files. Conversion engines, fonts or libraries may still be downloaded by the page so the tool can run.

Frequently asked questions

Is this MP4 to MKV converter free?

Yes. The converter is free to use for common personal and everyday file conversion tasks.

Will conversion improve quality?

Changing format does not recreate missing detail. The best result comes from starting with the highest-quality original file you have.

Why did my conversion fail?

Failures usually happen because of unsupported codecs, damaged files, browser memory limits or very large files. Try a smaller file or a modern desktop browser.