How do I convert FLV to MP4?

Add your FLV file to the upload area above, then press Convert. The MP4 file downloads straight to your device. You do not need an account, and there is no watermark.

Are my files uploaded to a server?

No. This conversion runs entirely inside your browser using WebAssembly, so the file never leaves your device — you can even disconnect from the internet after the page loads and it will still work.

Does converting to MP4 reduce quality?

MP4 uses lossy compression, so some data is discarded. At the default quality the difference is very hard to see or hear; raise the quality setting if you need to be certain, at the cost of a larger file.

How large a file can I convert?

Up to 512 MB per file for this conversion. Because the work happens in your browser, the practical limit is your device's memory — larger files work on a desktop with plenty of RAM and may fail on an older phone.

Can I convert several files at once?

Yes. Add as many as you like and press Convert All. Each file is processed independently, so one failure does not stop the rest, and you can download everything together as a ZIP.

Can I use this on my phone?

Yes. FileTools360 works in mobile browsers on iOS and Android, including choosing files straight from your camera roll. Very large videos may run out of memory on a phone — those are better converted on a laptop.

VideoAdjustable qualityRuns in your browser

FLV to MP4 Converter

Turn FLV files into MP4 in a couple of clicks. Obsolete Flash container. Convert to MP4 to keep it playable. The default video container of the internet. The output is re-encoded, so quality depends on the settings you choose.

On your deviceNever uploadedGone when you close the tabHow this works

Drop your files here

FLV files (.flv) · up to 512 MB each

or paste files from your clipboard

Ready when you are

Drop a FLV file above and FileTools360 will turn it into MP4 — right here on your device, without uploading anything.

⌘K to search converters

How to use it

1
Add your FLV files
Drag them onto the upload area, choose them from your device, or paste them from your clipboard. You can queue several at once.
2
Adjust the settings if you want to
The defaults suit most people. Open Advanced to control codec, resolution and bitrate, the audio track and start and end times.
3
Convert and download
Press Convert. Everything happens on your own device — nothing is uploaded. Download files one by one, or grab them all as a ZIP.

FLV and MP4 explained

FLV was the container behind Flash video, which dominated online video until browsers removed Flash support entirely at the end of 2020. Nothing plays FLV natively today.

MP4 is a container, not a codec. It usually holds H.264 video and AAC audio, and that specific combination is the closest thing the internet has to a universal video format.

Where FLV files come from: Video downloaded or archived from the web before roughly 2015.
Where MP4 is used: Phone cameras, screen recorders, and every video streaming platform.

FLV vs MP4

The two formats solve different problems, which is why converting between them involves trade-offs rather than a straight upgrade.

FLV compared with MP4
Property	Source	Target
Compression	Container (depends on codec)	Container (depends on codec)
Animation	Yes	Yes
Introduced	2002	2001
Browser support	Effectively dead — nothing plays it natively any more.	Plays on effectively every device.

FLV is stronger at: Historically small files for their era.
MP4 is stronger at: Plays on effectively every device and browser without extra software. Supported by every editor, platform and social network. Efficient compression with H.264 or H.265.

Why convert FLV to MP4?

People make this switch when they run into the limits of FLV: always. If you have FLV files, convert them before the tooling to read them disappears entirely. MP4 is the better fit when you want the video to simply play, anywhere, for anyone.

FLV limitations that prompt the switch: Effectively dead — no browser or modern player supports it. Low quality ceiling by current standards.
What you give up: H.264 carries patent licensing obligations for commercial distribution at scale. Less flexible than MKV for multiple audio tracks and subtitles.

Does converting FLV to MP4 reduce quality?

Both formats store the content without discarding data, so this conversion preserves it exactly. The file size may change because the two formats compress differently, but the content itself is unaffected.

“MP4” tells you nothing about quality. An MP4 can hold anything from a pristine 4K master to a heavily compressed clip.