How to convert AVI to MP4
Drop your AVI files into the box above, or click Choose files. You can add several at once.
Choose a quality. It only matters if the video has to be re-encoded; compatible videos are copied without any loss.
Click Convert to MP4. Files are processed on your device; a few minutes of media usually takes seconds.
Download the MP4 files one by one, or all at once as a ZIP.
Why convert AVI to MP4?
AVI is Microsoft's video format from the 1990s. It was everywhere in the Xvid and DivX era, but phones, browsers, WhatsApp, Instagram and most upload forms don't accept it today.
MP4 with H.264 video and AAC sound plays on every device and app, so converting old films and family videos keeps them watchable and easy to share.
Home videos are personal. Here they're converted on your own device, with nothing uploaded to a server.
AVI vs MP4
AVI is only a container. Inside is usually Xvid or DivX (MPEG-4 Part 2) video with MP3 or AC-3 sound, or Motion JPEG with uncompressed sound from cameras. None of these play natively on phones or in browsers.
The conversion re-encodes the picture to H.264 and the sound to AAC, usually giving a smaller file at the same visible quality. If the AVI already holds H.264 video, it's copied without re-encoding.
| Property | AVI | MP4 |
|---|---|---|
| Typical video codec | Xvid or DivX (MPEG-4 Part 2), MJPEG from older cameras | H.264 (AVC), sometimes H.265 or AV1 |
| Typical audio codec | MP3, AC-3 or uncompressed PCM | AAC |
| File size | Large for its quality: older codecs | Efficient |
| Best for | Old films, camera clips and DVD rips | Sharing and uploading video anywhere |
| Support | VLC and Windows players; not browsers, iPhones or most websites | Every phone, browser, TV and editing app |
Is it safe?
Yes. AVI to MP4 runs entirely in your browser. Your files are read and converted by your own device using built-in browser technology, so they are never uploaded to a server and nobody else can see them.
You can check this yourself: open your browser's developer tools, switch to the Network tab and convert a file. No upload requests are made.
AVI and WMV are opened by FFmpeg, the open-source engine behind VLC and most video tools, compiled to run inside your browser. It's downloaded once (about 10 MB) the first time you convert one of these files. Your video is read and converted on your device and never uploaded.
Files stay in this tab's memory only until you remove them or close the page.
Frequently Asked Questions
Will my AVI play on my phone after converting?
Yes. The MP4 uses H.264 video and AAC audio, the combination every iPhone, Android phone, TV, browser and messaging app supports.
Does converting lose quality?
Re-encoding always changes the picture slightly, but at the default High quality the difference isn't visible, and H.264 is more efficient than Xvid or DivX, so the file often gets smaller too. H.264 AVIs are copied unchanged.
Why is this slower than MOV or MKV to MP4?
Browsers can't read these older formats, so the video is decoded and re-encoded to H.264 by FFmpeg running on one core of your processor, without the graphics hardware the other video tools use. A typical standard-definition clip converts faster than it plays; a long HD film can take a while, and the progress bar shows how far along it is.
What about AVIs with AC-3 or uncompressed sound?
They work. Any sound track FFmpeg can read, including AC-3 from DVD rips and PCM from cameras, is converted to AAC. The first video and audio track are kept.
Is there a size limit?
Each video can be up to 1 GB. Files are read from disk in pieces, so they don't need to fit in memory, but very long videos take longer on slower devices.