FLV to MP4 — in your browser
FLV is the old Flash video container. Browsers don't play it. Most editors don't import it. Drop a .flv file here for an MP4 you can actually use.
drop a .flv file here
or click to choose
FLV, briefly
FLV (Flash Video) was Adobe's container format for web video, dominant from 2002 to roughly 2015. Inside is typically H.264 (or older Sorenson Spark / VP6) video and MP3 or AAC audio. The container is the only part that's outdated; modern FLV files usually contain H.264 + AAC which transfer cleanly to MP4 without re-encoding.
Where you still find FLV files
- Old downloaded videos archived from the 2000s.
- Twitch VODs (the legacy ones — new ones are MP4).
- Stream captures from RTMP via OBS's older "Save to FLV" option.
- Old e-learning material burned to FLV by enterprise LMS systems.
Remux when you can, re-encode when you must
If the FLV has H.264 + AAC inside, remux is instant and lossless. If it has older Sorenson / VP6 video, we have to re-encode to H.264 because MP4 won't accept those codecs. The tool tries remux first.
FAQ
Will I lose quality?
Remux: no. Re-encode (only for old codecs): minor — we use CRF 18 (near-lossless) by default.
Why is FLV obsolete?
Flash Player was deprecated end of 2020. Browsers stopped supporting it. FLV the container has no future even though H.264 the codec inside is still current.
Does the file get uploaded anywhere?
No. The conversion runs in WebAssembly in your browser. Disconnect after loading to verify.