Why FLV files still exist despite Flash being discontinued
FLV (Flash Video) was the dominant format for online video streaming through most of the 2000s and early 2010s, back when Adobe Flash Player was how the overwhelming majority of web video was delivered — old downloaded videos, archived web content, and recordings from that era frequently exist as FLV files that were never converted when the format fell out of use. Flash Player itself was officially discontinued in 2020, and browser and OS support for playing Flash-era formats natively has largely disappeared along with it.
This leaves a real practical problem: FLV files that were perfectly normal a decade ago are now stranded, often unplayable in current browsers and increasingly unsupported by modern media players and editing software.
What's actually inside an FLV file
FLV typically contains H.263 or older variants of H.264 video with MP3 or AAC audio — codecs that were reasonable choices during Flash's era but have since been superseded by more efficient modern encoding. Converting to MP4 with current H.264 encoding settings often produces a file that's smaller than the original FLV while looking just as good or better, since encoding efficiency has genuinely improved since these files were originally created.
Where old FLV files tend to turn up
Video downloaded from websites during the Flash era, archived recordings from video hosting services that have since moved to different formats, and personal video collections from the 2000s and early 2010s are the most common places FLV files still surface today. If you're going through old digital archives or recovering content from an old hard drive, FLV is a reasonably likely format to encounter among the older files.
Converting once, permanently, saves future headaches
Since FLV support is only going to continue declining as software moves further past the Flash era, converting old FLV files to MP4 now — rather than waiting until they become completely unplayable — is a reasonable piece of digital housekeeping if you have content in this format that you actually want to preserve access to long-term. MP4's broad, stable support makes it a safer long-term storage format than a container tied to discontinued software.