What FLV is today
FLV (Flash Video) was the format behind most online video in the 2000s, when sites played clips through Adobe Flash Player. Flash reached its end of life in 2020, and current browsers no longer play FLV on web pages. The format did not disappear, though. It is still used inside live streaming systems based on RTMP, in older video platforms and in many archives of e-learning courses and web projects from that time.
Desktop players such as VLC, MPV and PotPlayer still open FLV files without any extra software.
Reasons to convert MP4 to FLV
- A streaming server, encoder or playout tool expects FLV input.
- You maintain an old website, kiosk or training package with a Flash-era player that only loads .flv.
- A legacy editing or presentation program on an old computer accepts FLV but not MP4.
- You need to replace a damaged FLV in an archive with a new file of the same type.
Codecs inside FLV
Early FLV files used the Sorenson Spark or On2 VP6 codecs. Later versions of the format added H.264 video with AAC audio, the same pair that most MP4 files use. That is why modern FLV files keep good quality at a reasonable size. The conversion is done by a built-in converter engine that runs locally in your browser. It is slower than the tools for modern formats, so give long videos some time and keep the tab open.
Avoiding common issues
- Old players show only black or green frames. Very old Flash players may not support H.264. Ask which codec the system expects before you convert a large batch.
- Audio and video drift apart. Set a constant frame rate, such as 25 or 30 fps, especially for phone recordings.
- The file is too large for the server. Lower the resolution or use the FLV compressor.
- To move an old FLV clip back to a format that plays in browsers and on phones, use FLV to MP4. Other options are on the MP4 converter page.