Click to choose an FLV or drop it here
FLV in, MP4 out — converted in your browser, never uploaded. F4V and other video types work too.Video and audio are processed in your browser by FFmpeg (ffmpeg.wasm), free software under the GPL-2.0-or-later and MIT licenses — licenses & source.
About converting FLV to MP4
To convert FLV to MP4, drop your .flv file on the box above and press Convert to MP4. The page looks inside the file first. If it holds H.264 video — most newer FLV files do — the video is repacked into an MP4 in a few seconds, with no quality loss. Older Flash videos are re-encoded.
FLV files come from two places today. Old ones are Flash videos from the 2000s, saved from web pages or old cameras. New ones are recordings of live streams and screen recordings: OBS Studio could save FLV, and many stream recorders still do. Both kinds play badly on phones, Macs and in video editors.
Everything runs in your browser. Your video is never uploaded.
Features
- Fast repack — H.264 video goes into the MP4 untouched, in seconds
- No quality loss on a repack — the picture is bit-for-bit the original
- Old Flash videos too — Sorenson Spark and On2 VP6 are re-encoded to H.264
- Sound fixed for you — AAC and MP3 are kept; other sound is turned into AAC
- Honest result — the page tells you if it repacked or re-encoded
- Optional resize — 1080p, 720p or 480p, if you also want a smaller file
- Private — no upload, no sign-up, no watermark
What is an FLV file?
FLV means Flash Video. Macromedia made it for the Flash Player in 2002, and Adobe kept it. For years almost every video on the web was an FLV, played by Flash inside the page. Adobe ended Flash Player on 31 December 2020, and browsers removed it.
The FLV container lived on in live streaming: the RTMP protocol that sends a stream to a server uses FLV inside. That is why stream recorders and older OBS versions save .flv files.
What is inside your FLV decides the speed
| Video inside the FLV | Where it comes from | What this page does | Time |
|---|---|---|---|
| H.264 with AAC or MP3 sound | OBS, stream recorders, Flash videos after 2007 | Repacks it untouched | Seconds |
| H.264 with other sound | Some recorders | Repacks the picture, turns the sound into AAC | Seconds to a minute |
| Sorenson Spark (H.263) | The first Flash videos, 2002–2005 | Re-encodes to H.264 | About as long as the video |
| On2 VP6 | Flash videos 2005–2008 | Re-encodes to H.264 | About as long as the video |
The page does this check for you and says what it did when the MP4 is ready.
Changing the resolution always means re-encoding, so leave it on *Keep the original* if you only want a fast MP4.
OBS recordings: why convert them?
Many people record in FLV (or MKV) on purpose: if the computer crashes during a long recording, the file is still readable up to the crash. An MP4 that was not closed properly can be lost.
After the recording, you need an MP4 for your editor, your phone or an upload. This page does what OBS calls remux: it moves the H.264 video and AAC sound into an MP4 without changing them. A 2-hour recording takes seconds to a minute, not hours. (A very big file needs enough memory in the browser: up to about 1–2 GB works on most computers.)
Frequently asked questions
How do I convert FLV to MP4 without losing quality?
Keep the repack option ticked and the resolution on *Keep the original*. If the FLV holds H.264 video (OBS and most stream recordings do), it is repacked into the MP4 untouched — the picture is exactly the same.
Why is my FLV converting slowly?
The video inside is an old Flash format (Sorenson Spark or VP6). No MP4 player plays those, so the page has to re-encode it, and that runs on your own computer. The page says *Re-encoding* when this happens. These old files are usually small, so they still finish fast.
Can I play an FLV on an iPhone or Mac?
Not with the apps that come with them. Convert it to MP4 here first; then it plays on iPhone, iPad and Mac, and in iMovie.
Do I still need Flash Player to watch FLV files?
No. Flash Player is gone, and you do not need it. VLC plays FLV files, and after you convert to MP4 every normal player does.
Is there a file size limit?
There is no upload, so there is no upload limit. The limit is your browser's memory: files up to about 1–2 GB usually work on a computer. Phones handle less.
Is my video uploaded?
No. The converter (ffmpeg) runs inside your browser, on your device. The video never leaves it.
Related tools
- MKV to MP4 — the other common OBS recording format
- WMV to MP4 — for old Windows Media videos
- Video Converter — convert to MP4, WebM or MKV from many formats
- Trim Video — cut the start and end of a long recording
- Compress Video to Size — make the MP4 fit an upload limit
Credits
Conversion is powered by ffmpeg.wasm (FFmpeg and x264, licensed under GPL-2.0).
How to use it
- Click the box and choose your FLV, or drag it onto the box
- Leave the repack option ticked — it makes the conversion take seconds when it can
- Leave Resolution on *Keep the original* unless you also want a smaller file
- Press Convert to MP4 and read the message: it says if it repacked or re-encoded
- Play the result, then press Download MP4
