NUT Converter
FileFlip converts NUT files into 30 other formats entirely inside your browser, using FFmpeg and WebCodecs compiled to WebAssembly. The NUT file is never uploaded to a server: it is read off your disk, converted on your own machine, and saved back by the browser. There is no file-size limit and no account to create.
How do I convert a NUT file?#
- Drop your NUT file onto the converter at the top of this page, or click it to pick one from your computer.
- Choose the format you want out of it. FileFlip downloads the engine that conversion needs, once, and your browser caches it.
- Conversion starts the moment you pick the format, and the result is yours to download. The work happens in this tab, so nothing is uploaded and nothing is queued.
Is it safe to convert NUT files online?#
Yes, because nothing is uploaded. FileFlip converts NUT files inside the browser tab you already have open, using WebAssembly builds of the same engines a desktop converter would install. Your file is read from your own disk into the page's memory, and no request carrying it is ever made.
You do not have to take that on trust. Open your browser's network panel, run a conversion, and you will see the engine come down and your file go nowhere. There is no upload, no server-side copy, no retention window, and no account tied to what you converted.
How FileFlip works lists every engine, its version and its download size, and shows how to check for yourself that nothing leaves your machine.
What happens to a NUT file#
FileFlip converts NUT into 30 formats with FFmpeg and WebCodecs, all of it inside the browser tab. Each conversion below names the engine it uses, what it downloads, and exactly what that conversion keeps or drops.
| Category | Video Files |
|---|---|
| File extension | .nut |
| FileFlip support | Read and written |
| Conversions available | 30 |
| Engines | FFmpeg and WebCodecs |
| Downloaded to your browser | 30.8 MB on the first conversion, then cached |
What is a NUT file?#
A NUT file is a general-purpose media container created inside the FFmpeg and MPlayer projects, built as a simple, open, patent-free alternative to AVI and similar formats, and able to wrap any codec those tools support.
NUT is worth using only inside an FFmpeg-based pipeline, such as a test harness or a tool chain that already standardises on it.
Convert NUT to MP4 or MKV for anything that needs to open outside FFmpeg or a player built on its libraries, since almost no other software recognises the container.
The NUT file format reference covers the specification, the programs that open one, and what each conversion keeps or drops.
NUT questions people ask#
What opens a NUT file?
ffplay and mpv both open NUT files directly, since both are built on FFmpeg's own libavformat library, which is where the NUT container comes from. Outside that ecosystem, support is essentially nonexistent.
Why would a file be in NUT instead of MP4 or MKV?
NUT usually turns up as the output of an FFmpeg-based tool or test pipeline rather than something a person chose deliberately, since it was designed as an open, patent-free container within the FFmpeg and MPlayer projects. Matroska ended up filling the same role for everyone else.
Is NUT related to Matroska or AVI?
NUT was designed around the same time as Matroska and for a similar reason, as a flexible, open alternative to AVI's limitations, but the two are independent formats with no shared structure. Matroska is the one that ended up widely adopted; NUT stayed inside the FFmpeg and MPlayer projects that built it.