How to use the MP4 to FLV converter
- Choose your MP4 video or drop it on the box.
- Check the settings. "Same as original" resolution is fastest. Lower it to 720p for a smaller file.
- Click "Convert to FLV". A progress meter shows how far along it is.
- Download your FLV.
Why convert MP4 to FLV?
A few RTMP streaming tools and legacy Flash archives still expect FLV. MP4 to FLV keeps H.264 video and AAC sound in a Flash Video container.
- MP4: usually lossy, so quality drops a little each time it is re-encoded.
- FLV: small files.
- FLV: still used for some streaming workflows.
Since the codecs are the same, the video is copied rather than re-encoded.
MP4 vs FLV
| MP4 | FLV | |
|---|---|---|
| Full name | MPEG-4 Part 14 | Flash Video |
| Type | Video | Video |
| Created by | Moving Picture Experts Group (MPEG) (2001) | Macromedia (later Adobe) (2003) |
| Compression | Lossy | Lossy |
| Typical codecs | H.264 + AAC | H.264 or Sorenson Spark + AAC or MP3 |
| Best for | Sharing videos online, phone recordings, social media uploads and streaming | Old web video archives and some RTMP live-stream recordings |
| Plays on | Windows, macOS, iPhone, Android, smart TVs, game consoles and every modern browser | VLC and some desktop players; browsers and phones no longer play FLV |
Does converting MP4 to FLV lose quality?
Often none. When the MP4 contains H.264 video, FLV can hold it as it is, so fast mode copies the streams without re-encoding. Other codecs 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 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.
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.
Frequently asked questions
Is the MP4 to FLV 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.
Are my files safe?
Yes. Files are converted locally in your browser and are never uploaded. When you close the page, nothing is left behind.
Will the FLV sound and look as good as the MP4?
Often none. When the MP4 contains H.264 video, FLV can hold it as it is, so fast mode copies the streams without re-encoding.
Can I convert FLV back to MP4?
Yes, use the FLV to MP4 converter.
An MP4 plays without sound. What should I do?
The audio may use a codec your player does not support (for example AC3). Convert it to MP4 again so the sound becomes AAC.
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.