Turn MP4 files into FLV
Turn your MP4 into an FLV. FLV is the usual choice for archived video from the Flash era of the web. Worth knowing: an FLV will not open in a browser tab, so it is a file for software rather than for the web. Your file never leaves your computer.
Need the other direction? Convert FLV to MP4
How to convert MP4 to FLV
- 1 Drop your MP4 .mp4 file onto the page, or click to browse for it.
- 2 Set the quality, or leave the default, which keeps the file small without anything showing.
- 3 Convert. The work happens on your own machine, so how long it takes depends on your computer and the file.
- 4 Download the FLV, or add more files and do the whole set in one go.
Why convert MP4 to FLV
- Small files and fast start-up over slow connections.
- Simple enough that conversion tools read it reliably.
- Old streaming captures.
- MP4: fussy about subtitle tracks and unusual audio tracks.
MP4 compared with FLV
How the two formats differ on the things that decide whether a conversion is worth making.
| Property | MP4 | FLV |
|---|---|---|
| File extension | .mp4 | .flv |
| Browser support | Every browser | No browser support |
| Introduced | 2001 | 2002 |
| Developed by | ISO/IEC MPEG | Adobe / Macromedia |
| Standard | Open | Proprietary |
Quality and what changes
Both formats are lossy, so this is a second generation of compression: the MP4 is decoded back to pixels that already carry its artefacts, and FLV then compresses that. The damage compounds rather than cancelling out, which is why repeated round trips visibly degrade an image. Encode at a higher quality than the source used, and convert once from the best copy you have rather than from an already converted file.
- Browsers will not display an FLV, so it downloads rather than opening in a tab.
- One FLV limitation to keep in mind: limited in what it can hold, with no modern features.
Questions about MP4 to FLV
Will converting MP4 to FLV lose quality?
A little. Both formats are lossy, so the file is decoded and compressed a second time and the two sets of artefacts add up. At a high quality setting the difference is hard to see, but avoid repeated round trips between lossy formats.
Can I open an FLV in a browser?
No. No mainstream browser renders FLV natively, so it will download rather than display. That is fine when the file is heading into desktop software or an archive, and a problem if it is going on a web page.
Is my MP4 file uploaded anywhere?
No. The whole thing runs inside the browser tab you already have open. Your MP4 is read straight from your own disk, converted on your machine and handed back as an FLV. Nothing is sent anywhere, nothing is stored and there is no account.
Is there a file size limit?
There is no server-side limit because no server sees the file. The real ceiling is your device memory, since the input and the output both have to fit in the tab. A few hundred megabytes is usually fine on a desktop machine and considerably less on a phone.
Can I convert several MP4 files at once?
Yes. Add as many as you like and they are processed one after another, then offered as separate FLV downloads or as a single ZIP. Speed depends on your own processor rather than on a queue.
Does the converter work offline?
Yes, after the page has loaded once. The engine is cached by the browser, so you can disconnect, reload and keep converting. That falls out of doing the work locally rather than being a separate mode you switch on.