FLV to MP4 converter
Convert FLV to MP4 in seconds, free and unlimited. No upload, no sign-up, no watermark: your video never leaves your device.
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Quick answer: To convert FLV to MP4, add the FLV file to the iHateFiles FLV to MP4 converter and press Convert. The conversion runs in your browser, so the file is never uploaded, and it is free with no sign-up, watermark or size limit. H.264 in an MP4 is the one combination that plays on essentially every device made this century.
Should you convert FLV to MP4?
Yes, if the FLV will not play where you need it. MP4 with H.264 plays on essentially everything, which is why nearly every other video format is converted to it.
The picture is re-encoded
An FLV usually holds Sorenson Spark, VP6 or H.264 from the Flash era. This writes H.264 video with AAC sound into the MP4. Both sides are compressed with loss, so this is a second generation: leave the quality at its default or higher, because the encoder is working from FLV artefacts rather than the original.
Expect a smaller MP4
H.264 video is a much more efficient codec than what an FLV holds, so at the same visual quality the MP4 is usually a third to a half of the size.
Where the MP4 will play
MP4 plays on every phone, laptop, TV, browser and messaging app.
FLV and MP4 side by side
| FLV | MP4 | |
|---|---|---|
| Inside the file | Sorenson Spark, VP6 or H.264 from the Flash era | H.264 video with AAC sound |
| Compression | Lossy | Lossy |
| Carries sound | Yes | Yes |
| Plays on | VLC and very little else since Flash was retired in 2020 | every phone, laptop, TV, browser and messaging app |
| Here | Read and write | Read and write |
What usually goes wrong
About the FLV. If you have FLV files they are probably old downloads worth rescuing, and converting them to MP4 is the way to keep them watchable.
About the MP4. Two MP4 files can behave completely differently depending on the codecs inside. A file that will not play is usually an unusual codec in an ordinary container, not a broken file.
How to convert FLV to MP4
- Add your FLV file. It is read from your disk and stays there.
- Check the settings. The output format is already set to MP4.
- Press convert and the MP4 file is saved back to your device.
MP4 converter: everything that converts to MP4
Questions
How do I convert FLV to MP4?
Open this page, add your FLV file, and press convert. The file is decoded and re-encoded by your own browser and saved back to your device. Nothing is uploaded.
Is this FLV to MP4 converter free?
Yes, completely. There is no account, no sign-in, no watermark and no daily limit, because there is no server doing the work. Your own device does it.
Are my files uploaded anywhere?
No. There is no upload endpoint. The conversion runs inside this browser tab, so your file never leaves your device. You can open your browser's network panel and watch: nothing carrying your file is sent.
Is there a file size limit?
No fixed limit. Because the work happens on your machine there is no server quota. The only ceiling is your own device's memory, which for video means very large files may be slow.
Will converting to MP4 lose quality?
MP4 is a lossy format, so some detail is discarded. The quality control on this page decides how much. The default is set high enough that most people cannot see the difference.
Can I convert several FLV files at once?
Yes. Add as many as you like and they are converted one after another, then offered as a single ZIP.