FLV to MP4
Convert FLV to MP4 so Flash-era clips and old stream recordings play again. H.264 inside is rewrapped in seconds; older codecs become H.264. Free, no sign-up.
- Free & unlimited
- No sign-up
- Files never uploaded
- No watermark
- Up to 2 GB per file
How to convert FLV to MP4 in three steps
No plug-in and no Flash Player needed. The converter loads into this tab and works on the file there.
- 1
Choose the .flv or .f4v file
Drop it onto the page or browse for it. Picking a file only reads it: you see its size, duration and resolution, and nothing starts until you click Convert.
- 2
Keep Fast Copy, or set the quality
For H.264 FLV files, keep Fast Copy to rewrap the video and AAC or MP3 sound, or pick Re-encode for fresh H.264 at High, Medium or Small file quality, with an optional step down to 1080p, 720p or 480p. Sorenson Spark or VP6 files get no mode choice: a note says the video will be re-encoded, and Quality and Resolution appear right away.
- 3
Save the MP4 and read the note
The MP4 keeps the old file name. The result screen puts the FLV size next to the new size. Which kind of FLV you have shows before you convert: older codecs get a note that the video will be re-encoded.
What this FLV to MP4 converter does inside the file
FLV files from 2003 and from 2015 look the same from outside. The codecs inside decide the outcome.
Later Flash video is rewrapped as is
Flash Player added H.264 in late 2007, and later Flash video often pairs it with AAC sound. When that stream is 8-bit 4:2:0 H.264, Fast Copy moves the frames into MP4 without touching them, so it takes seconds.
Sorenson Spark and VP6 get new H.264
Early clips use Sorenson Spark (a variant of H.263) or On2 VP6, which phones and browsers can't decode. That video is re-encoded to H.264 automatically. In our test a 6-second Sorenson FLV went from 393 KB to 101 KB in about 3 seconds.
MP3 soundtracks are kept
Most Flash-era audio is MP3 or AAC, and MP4 can hold both, so those tracks are copied as they are, unless you choose Re-encode, which converts every track to AAC. Any other audio track is converted to AAC at 192 kbps on its own.
No fake upscaling
Old web clips are often tiny, such as 320x240. Resolution choices only go down, and sizes at or above the source are greyed out, so the MP4 keeps its true size instead of a blurry blow-up.
Ready for an HTML5 video tag
The MP4 is written with its index at the start of the file. Put it on a web page in place of an old Flash player and it can begin playing before the download finishes.
Convert FLV to MP4: this tool, VLC, FFmpeg or upload sites
The methods search results recommend, and what each one does with an old Flash file.
| This converter | VLC Convert / Save | FFmpeg with -c copy | Upload converter sites | |
|---|---|---|---|---|
| Video leaves your computer | No | No | No | Yes, stored on their servers for a while |
| What you install | Nothing | The VLC app | FFmpeg, plus a terminal command | Nothing |
| H.264 FLV | Rewrapped, frames untouched | Re-encoded by the chosen profile | Rewrapped | Depends on the site |
| Sorenson Spark or VP6 FLV | Re-encoded to H.264 automatically | Re-encoded | Fails; needs -c:v libx264 instead | Depends on the site |
| MP3 audio | Copied | Re-encoded by the profile | Copied | Depends on the site |
| Folders of clips | One file at a time | Several files per run | Yes, with a loop script | Batch on many sites |
| Largest file | About 2 GB | Whatever your disk holds | Whatever your disk holds | Set by each service |
| Price | Free, no account | Free | Free | Depends on the service |
Who still needs to turn FLV to MP4
FLV was the web's video format for most of the 2000s, so it turns up in a lot of old folders.
Clips saved from Flash-era sites
Music videos, news segments and funny clips grabbed from video portals before they moved to HTML5. Many still sit on laptops as .flv files that a phone's built-in player won't open.
Old live stream archives
Early streaming setups and older OBS profiles often recorded straight to FLV. Converting the archive lets you cut highlights in a current editor or post them again.
E-learning and training material
Course modules built with Flash-era authoring tools often carry FLV clips. Current course tools and LMS players usually expect MP4, so convert the clips before you rebuild the lesson.
A website that used a Flash player
Flash Player was retired at the end of 2020, so embedded FLV players on old company or club sites now show nothing. Swap each FLV for an MP4 in a video tag.
Watching on a phone or TV
Phones, tablets and smart TVs rarely open FLV. An MP4 with H.264 and AAC is the version they are built to play.
Family videos on old drives and CDs
Camera clips that someone shrank to FLV for an early web album or forum post. Convert them once and they open like any other home video.
What is an FLV file, and is FLV outdated?
FLV stands for Flash Video. Macromedia, and later Adobe, used it to stream video through Flash Player, and for years most web video, from early video sites to news portals, played that way. Adobe stopped supporting Flash Player on December 31, 2020, and browsers removed it. The format is now outdated: it still holds video, but almost nothing plays it by default.
FLV and MP4 are both containers, the box around the video and audio. FLV was built for one plug-in and usually holds Sorenson Spark, VP6 or H.264. MP4 is an ISO standard that browsers, phones, TVs and editors read directly. When the file already holds H.264, going from FLV to MP4 is only a change of box; with the older codecs the video is encoded again.
FLV to MP4 mistakes that cost time or quality
Mistake: Renaming video.flv to video.mp4.
Do this instead: The name changes but the Flash container stays, so players that refused it still do. Convert the file instead.
Mistake: Hoping the MP4 will look sharper than the FLV.
Do this instead: Converting can't add detail a 2006 clip never had. Keep the original resolution; it is the best the source can give.
Mistake: Choosing Re-encode for an H.264 stream recording.
Do this instead: Fast Copy rewraps 8-bit 4:2:0 H.264 untouched in seconds. Re-encoding 1080p runs at about real time, so a two-hour broadcast would take about two hours.
Mistake: Running ffmpeg -c copy on an early Flash clip.
Do this instead: Stream copy only works when the FLV holds H.264 video. Sorenson Spark and VP6 need a re-encode, which this page does on its own.
Mistake: Feeding in a stream archive bigger than about 2 GB.
Do this instead: The browser runs out of memory past that point. Convert very long recordings with desktop FFmpeg instead.
Privacy, cost and limits of this FLV to MP4 tool
Old recordings stay private
Your file is converted on your own device and is never uploaded to our servers. Archived streams and family clips never sit on a stranger's server.
Free with no cap on files
No account, no watermark and no daily limit. Clips are converted one after another, not as a batch.
Up to about 2 GB per file
Browser memory sets the ceiling. A 1.6 GB MKV converted in our tests, while a 2.1 GB file stopped with an out-of-memory error.
Built on open-source FFmpeg
The engine is unmodified FFmpeg 5.1.4 compiled to WebAssembly. Your browser fetches it once from jsDelivr, about 32 MB, and reuses the cached copy afterwards.