Convert FLV to MP4
Convert a Flash video into an MP4 you can actually watch. FLV files were made to be played by the Flash plug-in inside a web page, and Adobe switched Flash off at the end of 2020 — browsers removed it entirely, so the player these files were built for no longer exists anywhere. The video inside is usually intact and often already H.264; what has gone is the thing that used to open it.
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Up to 50 MB. Deleted automatically after 30 minutes.
What it does
- Re-encoded to H.264 video and AAC audio
- Recovers video stranded by Flash's shutdown
- Handles both H.264 and older Sorenson payloads
- No watermark and no sign-up
How to use FLV to MP4
- 1
Add the FLV
Drop it in or choose it from your computer. Files up to 50 MB, and no account is needed.
- 2
Convert
The video and audio are decoded and rewritten as H.264 and AAC inside MP4, whichever codec the Flash file was using.
- 3
Watch it again
The MP4 opens in any player, any browser and on any phone — none of which will run Flash.
The player disappeared, not the video
FLV — Flash Video — was the format of web video for roughly a decade. Nearly every video site of the late 2000s served it, because the Flash plug-in was installed almost everywhere and could decode it inside a page, at a time when browsers themselves could not play video at all.
Adobe ended Flash Player on 31 December 2020, and browsers did not simply disable it, they removed it. That left a large number of perfectly good recordings with no software able to open them. It is an unusual kind of obsolescence: the files did not degrade and the codecs inside them are frequently still current. The runtime they depended on was switched off.
What is inside varies by age. Files from around 2003 to 2008 typically use Sorenson Spark or VP6 and look like video of that era. Later ones use H.264 — the same codec an MP4 uses today — which means the picture quality is fine and only the container is holding it back.
How it works
Whatever codec is present is decoded and written into an MP4 as H.264 video with AAC audio. For an older Sorenson or VP6 file this is a genuine re-encode with the usual small cost. For a later H.264 file the picture is being decoded and encoded again, which is not free either, but the practical difference is slight against the alternative of not being able to watch it at all.
If the file will not convert
A small number of FLV files are not really complete videos. Streaming sites sometimes served fragments, and a download interrupted partway leaves a file that looks right in a folder listing and has no usable end. If a conversion fails here with a decoding error, an incomplete download is the most likely explanation, and no converter will be able to do better with it.
Audio in old Flash video
Flash carried audio in whatever was convenient at the time, which in practice means MP3 in older files and AAC in later ones, occasionally at sample rates that modern players handle awkwardly. Very early FLV files sometimes use Nellymoser, a speech codec built for low-bandwidth voice, which sounds thin and metallic because that is what it was designed to be.
All of it is decoded and rewritten as AAC. A Nellymoser recording will still sound like a 2005 voice chat afterwards — converting cannot add information that was never captured — but it will play, which is the part that matters.
Keeping the original
FLV files are usually small, and they are the only copy of whatever they hold. Keep them alongside the conversion. Nothing about the original stops being readable by software in future; it is browsers that stopped, and a desktop tool like VLC or ffmpeg still opens FLV perfectly well today.
Examples
A downloaded lecture from a Flash-era site
Educational and conference video from the late 2000s was overwhelmingly Flash. Files saved at the time now have no player, though the recordings themselves are fine.
Old web video from a personal archive
Anything saved from a video site before roughly 2011 is likely to be FLV. Converting is the only route back to it now that no browser can run the plug-in.
Frequently asked questions
Why can I not play FLV files any more?
Because Adobe ended support for Flash Player on 31 December 2020, and the browsers removed the plug-in rather than leaving it disabled. FLV was designed to be decoded by Flash inside a web page, so when the runtime disappeared the format lost its player. The files were not deleted or damaged — the software that understood them was withdrawn.
Is the video inside still good?
Usually yes, and often better than people expect. Later FLV files carry H.264 video, the same codec MP4 uses, so the picture is thoroughly modern even though the wrapper is not. Earlier files use Sorenson Spark or VP6, which are genuinely dated and will look it, but both convert without trouble.
What is the difference between FLV and F4V?
F4V was Adobe's later format and is essentially MP4 with a different extension, introduced once Flash gained H.264 support. FLV is the original container from 2003. If your file is F4V, renaming it to .mp4 will often just work, which is not true of FLV — a real conversion is needed there.
Will this work on a file downloaded years ago?
That is exactly the case it is for. An FLV sitting in an old downloads folder is a complete, valid file; its only problem is that nothing left on your computer knows how to open it. Converting it produces something every player made in the last fifteen years can read.