Convert FLV to MP3
Get the audio out of a Flash video as an MP3. Flash was switched off at the end of 2020 and browsers removed the plug-in entirely, so FLV files have no player left — but the recording inside is usually intact, and if what you wanted was a talk, a lecture or a piece of music, the audio is the part worth rescuing.
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Up to 50 MB. Deleted automatically after 30 minutes.
What it does
- The video stream is discarded, not re-encoded
- Reads MP3, AAC and Nellymoser audio
- Recovers sound stranded by Flash's shutdown
- No watermark and no sign-up
How to use FLV to MP3
- 1
Add the FLV
Drop the file in or choose it from your computer. These files are usually small.
- 2
Convert
The video is dropped and whatever audio the Flash file holds — MP3, AAC, or an old speech codec — is re-encoded as MP3.
- 3
Play it again
The MP3 opens in anything, which is more than can be said for the file it came from.
The recordings survived; the player did not
FLV was the format of web video for roughly a decade, because the Flash plug-in was installed nearly everywhere and could decode video inside a page at a time when browsers themselves could not. Conference talks, lectures, live sessions, radio archives and an enormous amount of ordinary web video were all served this way.
Adobe ended Flash Player on 31 December 2020, and browsers removed it rather than disabling it. That left a large body of complete, undamaged recordings with nothing able to open them.
For a great deal of that material the pictures were never the point. A talk is a person at a lectern. A live session is often a static image. Extracting the audio recovers what anybody actually wanted, and the result is a format that will still open in twenty years.
How it works
The video track is discarded and the audio is decoded and re-encoded to MP3 at a high variable-bitrate setting. Because the frames are never processed, this is fast and the output is small.
What the source holds varies with its age, and all of it is read the same way: MP3 in mid-2000s files, AAC in later ones, and Nellymoser or Speex in the oldest.
Three eras of Flash audio
Files from roughly 2003 to 2007 usually carry MP3. Re-encoding one to MP3 is a second lossy pass, which costs a little; for speech it is not audible.
Files from about 2008 onward carry AAC, often at good bitrates because Flash by then was competing with proper video players. These convert cleanly and sound essentially the same afterwards.
The oldest material, and anything recorded from a microphone through Flash itself, may use Nellymoser. It was designed for live voice over dial-up connections, and it sounds like it. Converting makes the file playable and changes nothing about how it sounds, because the information was discarded when it was recorded.
Keep the original anyway
FLV files are small, and desktop software still reads them perfectly well — VLC and ffmpeg both open FLV today without complaint. It was browsers that stopped, not every piece of software in the world. Keeping the original costs almost nothing and leaves the door open if you later want the video after all.
Examples
A conference talk saved before Flash died
Talks and lectures from Flash-era sites are common in old download folders. The slides rarely matter afterwards; the speaker does.
Music from an old web video
Live sessions and radio recordings were served as FLV for years. The video was usually a static image anyway.
Frequently asked questions
Is the audio in an FLV any good?
It depends entirely on the era. Later files carry AAC at reasonable bitrates and sound fine. Files from the mid-2000s often carry MP3, which is also fine. The oldest ones use Nellymoser, a speech codec designed for voice chat over dial-up, and that sounds thin and metallic because that is precisely what it was built to be.
Why is extracting audio easier than watching the video?
Because the audio has somewhere to go. MP3 plays on everything, so once the sound is out of the Flash container the problem is over. The video is harder only in that it needs re-encoding to a modern codec — but if you never wanted the pictures, extracting the audio is both faster and the end of the job.
Can this recover a partially downloaded file?
Sometimes, and more often than for video. Streaming sites served FLV in fragments, and an interrupted download leaves a file with no proper ending. Audio decoding tends to degrade gracefully — you often get everything up to the point the download stopped, rather than nothing at all.
What was Nellymoser used for?
Voice chat. Flash could capture from a microphone and send it live, and Nellymoser was the codec built for that: extremely low bitrate, optimized for a single speaking voice, and indifferent to everything else. If an FLV recording of a webinar or a call sounds like a bad phone line, this is why, and no conversion improves it.