MP4 to MKV Converter
MKV (Matroska) is an open-source container that supports virtually unlimited audio, video, and subtitle tracks in a single file. Converting MP4 to MKV is ideal when you need advanced features like chapter markers, multiple audio languages, or soft subtitles that viewers can toggle on and off.
MP4 to MKV conversion is a lossless remuxing process. Both containers support the same codecs (H.264, H.265, AAC), so your video and audio data is simply repackaged without any transcoding or quality degradation.
How to Convert MP4 to MKV
- 1
Drop your MP4 file into the upload area or select it from your device.
- 2
Select MKV as the desired output format.
- 3
Hit Convert and download your MKV file once the process finishes.
MP4 vs MKV — Format Comparison
| Feature | MP4 | MKV |
|---|---|---|
| Full Name | MPEG-4 Part 14 | Matroska Video |
| Type | Video | Video |
| Codec | H.264 / H.265 / AV1 | H.264 / H.265 / VP9 / AV1 |
| Lossless | No | No |
| Extension | .mp4 | .mkv |
| Best For | Online video streaming | High-quality video archival |
MP4 Strengths
- Universal device and browser support
- Excellent compression-to-quality ratio
- Supports subtitles, chapters, and metadata
MKV Strengths
- Open standard with no licensing fees
- Supports unlimited tracks (audio, subtitles, video)
- Excellent for high-quality video with multiple languages
Frequently Asked Questions
When to Convert MP4 to MKV
- Archiving video collections with multiple audio and subtitle tracks
- Preparing media files for Plex, Kodi, or Jellyfin media servers
- Bundling chapter markers and metadata into a single video file
- Storing high-quality video with lossless audio tracks
Related Conversions
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Get Embed CodeAbout Our MP4 to MKV Converter
This converter uses FFmpeg compiled to WebAssembly (WASM) to transform your MP4 files into MKV format entirely inside your web browser. When you select a file for conversion, the processing happens locally on your device. Your file is never uploaded to any server, never transmitted over the internet, and never stored anywhere outside your own computer. This privacy-first architecture makes our tool safe for confidential and sensitive content — including legal recordings, medical files, financial presentations, personal media, and any other material you would not want on a third-party server.
The conversion process works by decoding the MP4 input using FFmpeg's highly optimized decoders, then encoding the output in MKV format with carefully tuned settings that balance quality and file size. When possible, the tool uses stream copy mode to remux (rewrap) compatible streams without re-encoding, which preserves the original quality with zero generational loss. When re-encoding is necessary due to codec differences between the two formats, the converter uses high-quality encoding settings to minimize any visible or audible quality reduction.
Supported input formats include MP4, MOV, AVI, MKV, and WebM for video, with automatic detection of the codecs and parameters inside your source file. The output is optimized for maximum compatibility with modern devices and platforms including Windows, macOS, Linux, iOS, Android, smart TVs, and all major web browsers.
Why browser-based conversion is safer: traditional online converters require you to upload your file to a remote server, where it is processed by third-party infrastructure and then made available for download. This workflow exposes your data to interception during upload, unauthorized access on the server, unclear data retention policies, and potential data breaches. Professionals in regulated industries such as healthcare (HIPAA), legal (attorney-client privilege), and finance (SOX, GDPR) often cannot use server-based converters without violating compliance requirements. Our WebAssembly-powered approach eliminates all of these risks by ensuring your data never leaves the browser sandbox on your own device.
The tool handles files up to 500 MB on desktop browsers and 200 MB on mobile devices. No account registration, no software installation, and no recurring subscription is required. Conversion typically completes in seconds for small files and a few minutes for larger ones, depending on your device's processing capabilities. Once the conversion is finished, you can download the result immediately and the source data is discarded from browser memory.