MP4 to AVI Converter
FileFlip converts MP4 to AVI entirely inside your browser, using FFmpeg compiled to WebAssembly. The file is never uploaded to a server: it is read off your disk, converted on your own machine, and saved back by the browser. That means no file-size limit, no queue and no account.
How do I convert an MP4 file to AVI?#
- Drop your MP4 file onto the converter at the top of this page, or click it to pick one from your computer. You can add as many as you like.
- Leave the target set to AVI and the conversion starts on its own. FileFlip downloads 30.8 MB of WebAssembly the first time and nothing after that, then runs FFmpeg on your own machine.
- Save the AVI file. Your browser writes it straight to your downloads folder, because there was never a server holding it.
Does converting MP4 to AVI lose quality?#
It depends on what is inside the file. MP4 is a container rather than a codec, so whether the AVI conversion copies the streams across untouched or re-encodes them is decided by the codecs that particular file happens to use.
Is it safe to convert MP4 files online?#
Yes, because nothing is uploaded. FileFlip converts MP4 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 MP4 to AVI actually does to the file#
Converting MP4 to AVI runs on FFmpeg, downloads 30.8 MB of WebAssembly the first time and nothing after that, re-encodes or copies through depending on the codecs in the file, and drops encoded streams.
| Engine | FFmpeg |
|---|---|
| Conversion path | One step: MP4 → AVI |
| Downloaded to your browser | 30.8 MB, once, then cached by your browser |
| Quality | Decided by the codecs inside the file |
| You get back | One file |
| Where it runs | In a background worker, so the page stays responsive |
What survives the conversion
| What is in the file | This conversion | Why |
|---|---|---|
| Encoded streams | Dropped | The target format has nowhere to put it. |
What is an MP4 file?#
An MP4 file holds video, audio, subtitle and chapter tracks together in the MPEG-4 Part 14 container, the structure ISO standardised from Apple's QuickTime format and the way most video is stored and shared today.
Choose MP4 when the file has to play somewhere you do not control, which covers anything uploaded, emailed or handed to another person.
Convert an MP4 to something else when the destination is not a player: pulling out the audio, making a GIF, or moving into Matroska to keep several subtitle and audio tracks in one file.
What is an AVI file?#
An AVI file interleaves video and audio in chunks of Microsoft's RIFF structure, the container Windows has used for video since 1992 and the one most video from the DivX and Xvid years is stored in.
Keep a file as AVI when it is going into software old enough to predate MP4, which is the one situation where the format's age helps.
Convert AVI to MP4 to get the video playing on phones, browsers and TVs, and to shrink it, since what is inside an AVI is usually a codec generation or two behind.
MP4 to AVI questions people ask#
Is MP4 a video format or a codec?
MP4 is a container, not a codec. It is a wrapper holding video, audio and subtitle streams side by side, and the codec inside decides whether a device can actually decode it. Two MP4 files can behave completely differently: one holding H.264 plays everywhere, one holding H.265 or AV1 may not play at all on older hardware.
Why won't my MP4 file play?
An MP4 that refuses to play is almost always carrying a codec the player cannot decode rather than being damaged. H.265 and AV1 are the usual culprits, since both need recent hardware or software support, and some MP4s from streaming services are encrypted and will only open in an authorised app. Re-encoding the video to H.264 fixes nearly all of these.
Does converting MKV to MP4 lose quality?
Converting MKV to MP4 loses nothing at all when the video is already H.264 or H.265 with AAC audio, because the streams are lifted out of one container and dropped into the other untouched. That is a remux, and it runs at disk speed. Quality only drops when the codec has to change, for example a VP9 video that MP4 players do not expect, which forces a full re-encode.
What is the difference between MP4 and MOV?
MP4 was standardised from Apple's QuickTime file format, which is what a MOV file uses, so the two share the same underlying atom structure. In practice this means an H.264 video in a MOV and the same video in an MP4 are the same bytes in a slightly different wrapper, and converting between them is a fast remux rather than a re-encode. MOV also carries codecs MP4 does not, ProRes being the common one.