MKV is the format people choose when they want one file to hold everything: the picture, several sound tracks and subtitles. If your video is an MP4 and your media server, archive or editing setup wants Matroska, you need a quick way across.
This page lets you convert MP4 to MKV right in your browser. The video is not uploaded, and for most files nothing is re-encoded. Read on for how the conversion works, what it can and cannot do for you, and when MKV is a sensible choice.
How to convert MP4 to MKV
- Drop your .mp4 or .m4v file onto the tool above.
- Make sure "Convert to" shows MKV. The tile reads "Matroska, keeps every track".
- Leave Quality alone if you see the note that the video is copied as it is.
- Keep the sound switched on with "Keep the sound".
- Press Convert and save your MKV, or download several files as a zip.
It is free, with no account and no watermark. Video tools do not count toward the free daily limit, which covers document conversions only.
What Matroska offers that MP4 does not
Matroska is an open container made to be flexible. It can hold many tracks in one file, so a single MKV can carry a picture, a few languages of sound and a set of subtitle tracks. It also copes with an unusually wide range of picture and sound formats, which is why it is popular for archives and downloaded video.
MP4 is more limited, but far more widely accepted on phones, televisions and web forms. Both formats can carry the same H.264 picture, so the choice is less about quality and more about what the receiving software expects. The two are good at different things, as our MKV vs MP4 guide sets out, and moving a file from MP4 to MKV only makes sense when the destination understands Matroska.
| Situation | Better choice |
|---|---|
| Sharing with friends or posting online | MP4 |
| Playing on a TV or phone | MP4 |
| Building a personal media library with several tracks | MKV |
| Archiving a video in a flexible, open container | MKV |
| A media app or editor that asks for Matroska | MKV |
Does MP4 to MKV keep the quality?
Usually, yes, though it depends on the file. The tool takes the picture and sound from the MP4 and writes them into a Matroska container as they are. When that happens, the Quality control shows "This video is copied as it is into the new format, so the quality does not change it." The job is fast, even for a large file, because nothing is rebuilt. That is the main appeal of this page: you can change the container of a long recording in a short time, without paying for it in picture quality.
One thing to understand: a repackage does not add tracks. Moving to MKV gives the file a container that can hold more, but it will only contain what the MP4 had. If you want extra audio or subtitles, you would add them with other tools, for example add audio to video for a sound track.
When the picture is re-encoded
If the tool cannot copy the picture as it is, it encodes it again, and Quality starts to matter. Balanced stays visually close to the original, Smaller makes a lighter file and Best keeps the most detail. The estimated size under each option helps you choose. Because a re-encode is real work for your processor, a long clip will take longer than a repackage would, so give it time and leave the tab where it is. The result is a normal MKV that opens in the same players and apps as any other.
Does the MKV file get smaller?
Not by much, if at all. A repackage keeps the same picture, so the file stays close to the original size. If your goal is a lighter file, use compress video instead, which is made for that.
Where an MKV file works and where it does not
Many desktop players, media servers and editors open Matroska happily. Phones, televisions, consoles and web upload forms are far less predictable. Think about where the file is going before you convert, and keep your MP4 as well. A small test helps: convert a short clip first, then try it in the player or app you plan to use. If it opens and plays with sound, convert the rest with confidence.
- Good fit: a home media server, a desktop player, a long-term personal archive.
- Risky: social apps, school portals, older TVs and car screens.
- Sensible habit: keep both files, and use the MKV only for the place that asked for it.
A note on names: the converted file keeps your original name and takes the .mkv ending. If you convert a file to the format it already has, the tool adds "_converted" to the name instead, so nothing is overwritten. That keeps a mixed folder of MP4 and MKV files easy to sort.
Before you delete anything, open the MKV in the program that asked for it and play a few seconds of the start, the middle and the end. A minute of checking now saves a long search later, and your original MP4 is still exactly where you left it.
If you find later that you need the MP4 again, the reverse conversion is on the MKV to MP4 page.
Speed, limits and privacy
An MP4 is handled the fast way, and there is no size limit. The note beside the Convert button reads "Fast, on this device. Nothing uploaded". Keep the tab open until the file is saved. If you have a whole folder of clips to move into a Matroska library, drop them in together, press Convert once and take the results as a single zip. The same settings apply to every file, which keeps the library consistent.
Your video is never uploaded, and the server does no video work. The privacy page has the details, and it matters for personal archives, which tend to hold exactly the kind of footage you would not want on another server. The tool works in current Chrome, Edge and Firefox. For other formats, see the main convert video page.
Move your MP4 into Matroska
To convert MP4 to MKV, drop your file into the tool above and press Convert. It is usually a quick repackage that keeps the picture as it is, and your clip stays on your computer.
Free, private and without a watermark, so start the conversion above. Your original MP4 is never changed, so keep it for sharing and use the MKV where a library or archive asks for Matroska.
