How do I convert MP4 to MKV?

Add your MP4 file to the upload area above, then press Convert. The MKV file downloads straight to your device. You do not need an account, and there is no watermark.

Are my files uploaded to a server?

No. This conversion runs entirely inside your browser using WebAssembly, so the file never leaves your device — you can even disconnect from the internet after the page loads and it will still work.

Does converting to MKV reduce quality?

MKV uses lossy compression, so some data is discarded. At the default quality the difference is very hard to see or hear; raise the quality setting if you need to be certain, at the cost of a larger file.

How large a file can I convert?

Up to 512 MB per file for this conversion. Because the work happens in your browser, the practical limit is your device's memory — larger files work on a desktop with plenty of RAM and may fail on an older phone.

Can I convert several files at once?

Yes. Add as many as you like and press Convert All. Each file is processed independently, so one failure does not stop the rest, and you can download everything together as a ZIP.

Can I use this on my phone?

Yes. FileTools360 works in mobile browsers on iOS and Android, including choosing files straight from your camera roll. Very large videos may run out of memory on a phone — those are better converted on a laptop.

VideoAdjustable qualityRuns in your browser

MP4 to MKV Converter

Turn MP4 files into MKV in a couple of clicks. The default video container of the internet. Flexible container that holds any codec, subtitles and tracks. The output is re-encoded, so quality depends on the settings you choose.

On your deviceNever uploadedGone when you close the tabHow this works

Drop your files here

MP4 files (.mp4, .m4v) · up to 512 MB each

or paste files from your clipboard

Ready when you are

Drop a MP4 file above and FileTools360 will turn it into MKV — right here on your device, without uploading anything.

⌘K to search converters

How to use it

1
Add your MP4 files
Drag them onto the upload area, choose them from your device, or paste them from your clipboard. You can queue several at once.
2
Adjust the settings if you want to
The defaults suit most people. Open Advanced to control codec, resolution and bitrate, the audio track and start and end times.
3
Convert and download
Press Convert. Everything happens on your own device — nothing is uploaded. Download files one by one, or grab them all as a ZIP.

MP4 and MKV explained

MP4 is a container, not a codec. It usually holds H.264 video and AAC audio, and that specific combination is the closest thing the internet has to a universal video format.

Matroska is a container designed to hold essentially anything: any codec, unlimited audio tracks, subtitle tracks, chapters and attachments in one file. It is the format of choice for archiving films with multiple languages.

Where MP4 files come from: Phone cameras, screen recorders, and every video streaming platform.
Where MKV is used: Media archives, anime and film collections, and high-quality recordings.

MP4 vs MKV

The two formats solve different problems, which is why converting between them involves trade-offs rather than a straight upgrade.

MP4 compared with MKV
Property	Source	Target
Compression	Container (depends on codec)	Container (depends on codec)
Animation	Yes	Yes
Introduced	2001	2002
Browser support	Plays on effectively every device.	Great in VLC and media servers, poor in browsers.

MP4 is stronger at: Plays on effectively every device and browser without extra software. Supported by every editor, platform and social network. Efficient compression with H.264 or H.265.
MKV is stronger at: Holds any codec. Unlimited audio, subtitle and chapter tracks. Open and well documented.

Why convert MP4 to MKV?

People make this switch when they run into the limits of MP4: you need many embedded subtitle and audio tracks, where MKV is better suited. MKV is the better fit when archiving or watching in a capable player such as VLC or a media server.

MP4 limitations that prompt the switch: H.264 carries patent licensing obligations for commercial distribution at scale. Less flexible than MKV for multiple audio tracks and subtitles.
What you give up: Browsers will not play it. Many TVs, phones and editors reject it.

Does converting MP4 to MKV reduce quality?

Both formats store the content without discarding data, so this conversion preserves it exactly. The file size may change because the two formats compress differently, but the content itself is unaffected.

“MP4” tells you nothing about quality. An MP4 can hold anything from a pristine 4K master to a heavily compressed clip.