How to use the FLV to MP4 converter
- Choose your FLV video or drop it on the box.
- Check the settings. "Same as original" resolution is fastest and lets fast mode copy compatible videos without re-encoding. Lower it to 720p for a smaller file.
- Click "Convert to MP4". A progress meter shows how far along it is.
- Download your MP4.
Why convert FLV to MP4?
FLV is a dead Flash format. MP4 gives the same video in a file every modern device plays.
- FLV: flash is discontinued.
- MP4: plays almost everywhere.
- MP4: good quality at small sizes with H.264.
Most later FLV files contain H.264 and AAC, so the conversion is a fast copy with no quality loss.
FLV vs MP4
| FLV | MP4 | |
|---|---|---|
| Full name | Flash Video | MPEG-4 Part 14 |
| Type | Video | Video |
| Created by | Macromedia (later Adobe) (2003) | Moving Picture Experts Group (MPEG) (2001) |
| Compression | Lossy | Lossy |
| Typical codecs | H.264 or Sorenson Spark + AAC or MP3 | H.264 + AAC |
| Best for | Old web video archives and some RTMP live-stream recordings | Sharing videos online, phone recordings, social media uploads and streaming |
| Plays on | VLC and some desktop players; browsers and phones no longer play FLV | Windows, macOS, iPhone, Android, smart TVs, game consoles and every modern browser |
Does converting FLV to MP4 lose quality?
Often none. When the FLV contains H.264 video, MP4 can hold it as it is, so fast mode copies the streams without re-encoding. Other codecs (including HEVC while "Play everywhere" is ticked) are re-encoded at "Balanced" quality, which looks the same as the original to most people.
How long does it take?
Seconds when fast mode applies, even for a full film. If the video must be re-encoded, expect a few minutes for a long HD video.
What is an FLV file?
FLV is the Flash Video container that powered YouTube and most web video until about 2015. Adobe ended Flash Player in 2020, but FLV is still used by some live-streaming and recording software.
What is an MP4 file?
MP4 is a container that usually holds H.264 or H.265 video with AAC sound. It is built on Apple's QuickTime file structure and became an ISO standard in 2001. Because almost every phone, browser, TV and editing app can play it, MP4 is the safest choice when you need a video to just work.
Frequently asked questions
Is the FLV to MP4 converter free?
Yes, completely free, with no sign-up and no watermark. Files up to 1 GB each can be converted, and there is no daily limit.
Is my file uploaded to a server?
No. The converter runs inside your browser using WebAssembly, so your file is processed on your own device and never sent to us or anyone else.
Will the MP4 sound and look as good as the FLV?
Often none. When the FLV contains H.264 video, MP4 can hold it as it is, so fast mode copies the streams without re-encoding.
Can I convert MP4 back to FLV?
Yes, use the MP4 to FLV converter.
An FLV will not play anywhere. What should I do?
Convert FLV to MP4. If it holds H.264, the conversion is a quick copy.
Does it work on iPhone and Android?
Yes, in Safari, Chrome and other modern mobile browsers. Short files work best on phones; for long or high-resolution videos a computer is faster.