MKV to FLV converter
Convert MKV to FLV in seconds, free and unlimited. No upload, no sign-up, no watermark: your video never leaves your device.
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Quick answer: To convert MKV to FLV, add the MKV file to the iHateFiles MKV to FLV converter and press Convert. The conversion runs in your browser, so the file is never uploaded, and it is free with no sign-up, watermark or size limit. Re-encodes the picture and sound into a FLV container.
Should you convert MKV to FLV?
Do this when something specifically needs FLV. The picture is re-encoded, so it costs a little quality; if all you need is a file that plays everywhere, MP4 is usually the better target.
The picture is re-encoded
An MKV usually holds almost any codec, often H.264 or H.265 with several audio and subtitle tracks. This writes Sorenson Spark (FLV1) video with MP3 sound into the FLV. Both sides are compressed with loss, so this is a second generation: leave the quality at its default or higher, because the encoder is working from MKV artefacts rather than the original.
Expect a larger FLV
FLV uses Sorenson Spark (FLV1) video, an older and less efficient codec than an MKV normally holds. Matching the look takes more bytes, so the file grows. Do it for compatibility with whatever needs FLV, not to save space.
Extra tracks may not survive
An MKV can carry several audio tracks and subtitle tracks. FLV holds one picture and one sound, so this conversion keeps the main video and the first audio track. If you need the subtitles, save them first with Extract Subtitles.
Where the FLV will play
FLV plays on VLC and very little else since Flash was retired in 2020.
MKV and FLV side by side
| MKV | FLV | |
|---|---|---|
| Inside the file | almost any codec, often H.264 or H.265 with several audio and subtitle tracks | Sorenson Spark (FLV1) video with MP3 sound |
| Compression | Lossy | Lossy |
| Carries sound | Yes | Yes |
| Plays on | VLC, Plex, most smart TVs and Android, but not the iPhone Photos app or QuickTime | VLC and very little else since Flash was retired in 2020 |
| Here | Read and write | Read and write |
What usually goes wrong
About the MKV. MKV and WEBM share a signature because WEBM is a restricted Matroska, so tools sometimes report one as the other. What matters is the codecs inside.
About the FLV. If you have FLV files they are probably old downloads worth rescuing, and converting them to MP4 is the way to keep them watchable.
How to convert MKV to FLV
- Add your MKV file. It is read from your disk and stays there.
- Check the settings. The output format is already set to FLV.
- Press convert and the FLV file is saved back to your device.
Questions
How do I convert MKV to FLV?
Open this page, add your MKV file, and press convert. The file is decoded and re-encoded by your own browser and saved back to your device. Nothing is uploaded.
Is this MKV to FLV converter free?
Yes, completely. There is no account, no sign-in, no watermark and no daily limit, because there is no server doing the work. Your own device does it.
Are my files uploaded anywhere?
No. There is no upload endpoint. The conversion runs inside this browser tab, so your file never leaves your device. You can open your browser's network panel and watch: nothing carrying your file is sent.
Is there a file size limit?
No fixed limit. Because the work happens on your machine there is no server quota. The only ceiling is your own device's memory, which for video means very large files may be slow.
Will converting to FLV lose quality?
FLV is a lossy format, so some detail is discarded. The quality control on this page decides how much. The default is set high enough that most people cannot see the difference.
Can I convert several MKV files at once?
Yes. Add as many as you like and they are converted one after another, then offered as a single ZIP.