FLV to MP4 Converter (Flash Video)
Convert FLV to MP4 without installing software. Flash Player is gone, but FLV and F4V files from old downloads, webcam sites and earlier OBS recordings are still around, and ProMedia opens them with an FFmpeg engine that runs in your browser. H.264 video inside an FLV is copied without loss; older Sorenson or VP6 video is re-encoded to H.264. Nothing is uploaded.
- Runs on your device
- FFmpeg
- WebCodecs · GPU
- Works offline
Updated
Drop your videos here
How to convert FLV to MP4
Step 1: Drop your FLV or F4V files on the box above.
Step 2: The FFmpeg engine (about 31 MB) downloads the first time and is cached after that.
Step 3: Press Convert. H.264 streams are copied; older codecs are re-encoded.
Step 4: Download the MP4 files, one by one or as a ZIP.
Good to know
Settings explained
- Quality
- Only used when a stream has to be re-encoded. Compatible streams are copied with no quality loss.
- Faster: Smaller file, quickest export
- Balanced: Good quality at a sensible size
- Best quality: Largest file, slowest export
- Video codec
- Automatic copies the original video stream when the new format can hold it, so there is no quality loss.
- Automatic: Best codec the format and your device support
- H.264 (AVC): Plays everywhere
- H.265 (HEVC): About 35% smaller, newer devices
- VP9: Web / WebM
- AV1: Smallest files, slowest to encode
- Always re-encode
- Off: compatible streams are copied instantly and losslessly. On: every stream is re-encoded, which can fix playback glitches.
Formats
Batch-friendly: add many files and they are processed one after another — if one fails, the rest still finish.
How it runs
- FFmpeg (when needed)
- Older formats and a few filters use FFmpeg compiled to WebAssembly. It downloads once (about 31 MB) the first time it is needed and is cached for offline use.
- Hardware video engine
- Video is decoded and encoded by your device’s media hardware through WebCodecs — usually several times faster than real time.
FLV vs MP4: which is better?
MP4 is better for anything you want to watch or share today. FLV was made for one player, Adobe Flash, and lost its home when Flash ended in 2020; MP4 plays in every browser, phone and TV and can carry the same H.264 video many later FLV files use.
| Feature | FLV (Flash Video) | MP4 |
|---|---|---|
| Made for | Adobe Flash Player streaming | Every modern player and device |
| Video codecs | Sorenson Spark, On2 VP6, H.264 | H.264, HEVC, AV1 |
| Audio codecs | MP3, AAC, Nellymoser | AAC |
| Plays in browsers today | No | Yes |
| Best for | Nothing new; archive only | Sharing, editing and playback |
What is an FLV file?
An FLV file is Flash Video, the format Adobe Flash Player used to stream video on websites through the 2000s. Early files carry Sorenson Spark or On2 VP6 video with MP3 audio; later ones carry H.264 and AAC. Adobe retired Flash Player at the end of 2020, so browsers no longer play FLV and phone galleries ignore it.
Can you convert FLV to MP4 without losing quality?
Yes, when the FLV holds H.264 video. ProMedia copies that stream into the MP4 unchanged and converts only audio that is not AAC. Sorenson Spark and VP6 cannot live in an MP4, so they are re-encoded to H.264 at a constant-quality setting.
| Track in the FLV | In the MP4 | Quality |
|---|---|---|
| H.264 video | Copied | Identical |
| Sorenson Spark or VP6 video | Re-encoded to H.264 (x264, CRF 27 at Balanced) | Near-identical |
| AAC audio | Copied | Identical |
| MP3 or Nellymoser audio | Converted to AAC, 128 kbps by default | Clean |
How to play FLV files today
Converting is the simplest fix: an MP4 plays in any browser, phone and TV. Desktop players such as VLC still open FLV, but browsers and phone galleries do not. For a folder of old clips, convert them all once and keep the MP4s.
Tips & troubleshooting
Converting old OBS recordings? You can also use OBS’s own File → Remux Recordings; for new recordings, OBS can save MKV or MP4 directly.
Want only the soundtrack, as in “FLV to MP3”? Use extract audio from video, which accepts FLV too.
FLV refuses to convert? It may be cut off mid-file; try repair video first.
Have AVI clips from the same era? AVI to MP4 handles DivX and Xvid the same way.
FLV to MP4 Converter FAQ
How do I convert FLV to MP4 for free?
Drop the FLV files on this page and press Convert. It costs nothing, needs no account and adds no watermark. The only download is the FFmpeg engine, once, which your browser keeps for next time and for offline use.
How do I convert FLV to MP4 on Mac?
Open this page in Safari or Chrome and drag the FLV files onto the drop zone. The engine decodes Flash Video on the Mac itself and saves an MP4 that QuickTime, Photos and iMovie open. No app needs installing.
How do I convert FLV to MP3?
Use extract audio from video with MP3 selected. It reads FLV through the same FFmpeg engine and saves only the soundtrack, at up to 320 kbps.
Is any quality lost?
Not when the FLV holds H.264, which is copied as-is. Sorenson Spark and VP6 video from early Flash files is re-encoded to H.264; at Balanced or Best quality the result looks the same as the source, which was usually low resolution to begin with.
Is your video uploaded anywhere?
No. Your video is processed by your own browser on your own device. There is no server that receives files, so nothing is uploaded, stored or shared. You can even switch to airplane mode once the page has loaded.