MKV Converter
FileFlip converts MKV files into 30 other formats entirely inside your browser, using WebCodecs and FFmpeg compiled to WebAssembly. The MKV file is never uploaded to a server: it is read off your disk, converted on your own machine, and saved back by the browser. There is no file-size limit and no account to create.
How do I convert an MKV file?#
- Drop your MKV file onto the converter at the top of this page, or click it to pick one from your computer.
- Choose the format you want out of it. FileFlip downloads the engine that conversion needs, once, and your browser caches it.
- Conversion starts the moment you pick the format, and the result is yours to download. The work happens in this tab, so nothing is uploaded and nothing is queued.
Is it safe to convert MKV files online?#
Yes, because nothing is uploaded. FileFlip converts MKV files inside the browser tab you already have open, using WebAssembly builds of the same engines a desktop converter would install. Your file is read from your own disk into the page's memory, and no request carrying it is ever made.
You do not have to take that on trust. Open your browser's network panel, run a conversion, and you will see the engine come down and your file go nowhere. There is no upload, no server-side copy, no retention window, and no account tied to what you converted.
How FileFlip works lists every engine, its version and its download size, and shows how to check for yourself that nothing leaves your machine.
What happens to a MKV file#
FileFlip converts MKV into 30 formats with WebCodecs and FFmpeg, all of it inside the browser tab. Each conversion below names the engine it uses, what it downloads, and exactly what that conversion keeps or drops.
| Category | Video Files |
|---|---|
| File extension | .mkv |
| FileFlip support | Read and written |
| Conversions available | 30 |
| Engines | WebCodecs and FFmpeg |
| Downloaded to your browser | 30.8 MB on the first conversion, then cached |
What is an MKV file?#
An MKV file is a Matroska container built on the EBML binary format, and it can hold any number of video, audio, subtitle and attachment tracks, encoded with essentially any codec, in a single file.
Use MKV when a video needs multiple audio tracks, several subtitle languages, or a codec MP4 doesn't accommodate, and it's staying on software you control, like a media server or a desktop player.
Convert MKV to MP4 when a file needs to play on a device that never added MKV support, since that's usually a hardware or software gap rather than anything wrong with the codec inside.
The MKV file format reference covers the specification, the programs that open one, and what each conversion keeps or drops.
MKV questions people ask#
Why won't my TV or game console play an MKV file?
MKV is just a container, so the refusal is almost always about the container itself rather than the codec inside it. A lot of hardware players, smart TVs, the PS5, some streaming boxes, never implemented support for parsing Matroska, even though they can decode the exact same H.264 or H.265 video when it's wrapped in an MP4.
Is MKV a video codec?
No, MKV is Matroska, a container format, not a codec. It doesn't encode video itself; it just holds whatever video, audio and subtitle tracks were put into it, which can use nearly any codec that exists.
Should I use MKV or MP4?
MP4 wins on compatibility, since it plays almost anywhere. MKV wins on flexibility, holding multiple audio and subtitle tracks, chapters and font attachments that MP4 either can't carry or supports less completely. Pick MKV for archiving or editing where you control playback, and MP4 for anything that needs to just work on an unfamiliar device.
Does converting MKV to MP4 lose quality?
Only if the codecs inside need to change. When an MKV already holds H.264 or H.265 video with AAC audio, moving it to MP4 is a remux, repackaging the same compressed data with nothing re-encoded and no quality lost. A subtitle track in ASS or PGS format has no direct equivalent in MP4 though, so that part either gets converted to a compatible format or dropped.
Can MKV files be streamed or does everything have to download first?
Matroska was designed with streaming in mind, with an index that lets a player seek and start playback without the whole file being present. In practice almost no commercial streaming service delivers video in MKV, since there's no DRM standard for it that content owners have adopted.