MKV to FLV Converter
FileFlip converts MKV to FLV entirely inside your browser, using FFmpeg compiled to WebAssembly. The file is never uploaded to a server: it is read off your disk, converted on your own machine, and saved back by the browser. That means no file-size limit, no queue and no account.
How do I convert an MKV file to FLV?#
- Drop your MKV file onto the converter at the top of this page, or click it to pick one from your computer. You can add as many as you like.
- Leave the target set to FLV and the conversion starts on its own. FileFlip downloads 30.8 MB of WebAssembly the first time and nothing after that, then runs FFmpeg on your own machine.
- Save the FLV file. Your browser writes it straight to your downloads folder, because there was never a server holding it.
Does converting MKV to FLV lose quality?#
It depends on what is inside the file. MKV is a container rather than a codec, so whether the FLV conversion copies the streams across untouched or re-encodes them is decided by the codecs that particular file happens to use.
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 MKV to FLV actually does to the file#
Converting MKV to FLV runs on FFmpeg, downloads 30.8 MB of WebAssembly the first time and nothing after that, re-encodes or copies through depending on the codecs in the file, and drops encoded streams.
| Engine | FFmpeg |
|---|---|
| Conversion path | One step: MKV → FLV |
| Downloaded to your browser | 30.8 MB, once, then cached by your browser |
| Quality | Decided by the codecs inside the file |
| You get back | One file |
| Where it runs | In a background worker, so the page stays responsive |
What survives the conversion
| What is in the file | This conversion | Why |
|---|---|---|
| Encoded streams | Dropped | The target format has nowhere to put it. |
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.
What is an FLV file?#
An FLV file holds video and audio in tagged chunks meant to be streamed to Adobe's Flash Player, which is the only thing that ever played the format natively and has not shipped since the end of 2020.
There is no reason to create an FLV now; the only sensible use is holding on to one as the untouched original of something you have already converted.
Convert FLV to MP4 as soon as you find one, since the wrapper is the only thing standing between you and video that still plays perfectly well.
MKV to FLV 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.