Converters AVI to MP4 converter
Bring old AVI footage from camcorders and 2000s-era files into MP4 that modern devices will actually play.
Anything but Original forces a re-encode.
Quality, if a re-encode is needed
Drag files here, or
Converted to MP4 on your device. The converter itself is a 9.8 MB download, once.
Ready. Runs locally on your device.
Your files stay on your device. The tool works directly in your browser, using your device to process your files. Nothing is sent to our servers, and we never receive, store, or see your files or figures.
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Cite this page
Reembun. (2026, August 12). AVI to MP4 converter. https://reembun.com/avi-to-mp4
How to use it
Add the AVI
Drop the file in. Old AVI files are often large, and none of that has to be uploaded here.
Wait for the engine once
The converter downloads the first time and is kept afterwards.
Convert
AVI usually holds older codecs, so this conversion normally re-encodes rather than repackages. Expect it to take longer than a MOV or MKV would.
Download the MP4
The result is playable on phones and in browsers, which is usually why an AVI needs converting at all.
AVI is a 1992 format, and it shows
Audio Video Interleave was introduced by Microsoft in 1992, when video on a computer meant a 320×240 window. It was extended repeatedly over the following fifteen years, and every extension was a workaround for something the format was never designed to do.
What it cannot do properly, and never could:
- Variable frame rate. Every phone in the world records VFR. AVI assumes a constant rate.
- Files over 4 GB, without a vendor-specific hack that half the software of the time ignored.
- Modern codecs. H.264 in an AVI is legal but unusual and inconsistently supported.
- Proper timestamping, which is why audio drift in old AVI files is so familiar.
Its era is preserved in the files themselves: camcorder footage, DivX and Xvid downloads from the 2000s, screen captures from software that has not been updated since. The video is often perfectly watchable. Nothing modern will open it.
Why this conversion is slower than the others
MOV and MKV files usually hold H.264, which MP4 takes without modification. AVI usually holds MPEG-4 Part 2, the codec that DivX and Xvid are both implementations of, which is a generation older.
That leaves two paths:
- Copy. MP4 can legally carry MPEG-4 Part 2, so where the audio also fits, the streams are copied and the job is fast. The tool tries this first and tells you when it worked.
- Re-encode. Where the audio is something MP4 cannot hold, or the video codec is one of AVI’s stranger inhabitants, every frame is decoded and compressed again as H.264. This is the slow path, and it is why AVI conversion has a reputation for taking a while.
A re-encode also produces a much smaller file, frequently a third of the original, because H.264 is far more efficient than the codecs it replaced.
Getting the best out of old footage
Old camcorder video has already been compressed once, by hardware that was doing its best in 2006. Compressing it hard a second time is what makes it look genuinely bad.
- Set quality to High for anything you care about. The file will still be smaller than the AVI.
- Leave the resolution at Original. Footage shot at 640×480 gains nothing from being resized and loses detail it cannot spare.
- Convert from the original file, not from a copy someone already converted.
Nothing is uploaded
Home videos are exactly the category of file that should not be handed to an unknown server. This converter runs FFmpeg inside your browser tab, so the footage is read from your disk, converted by your processor, and written straight back. Nothing is transmitted to a server at any point.
Common questions
Why does AVI to MP4 take longer than MOV to MP4?
Because it usually cannot be a straight copy. Most AVI files hold MPEG-4 Part 2 video, better known as DivX or Xvid, sometimes alongside MP3 audio. That combination can be repackaged in some cases and has to be re-encoded to H.264 in others, and re-encoding means decoding and compressing every frame. Budget a minute or two per minute of video.
Will the video look worse afterwards?
Slightly, when a re-encode is needed, but usually less than people expect. Set the quality to High and the difference will be invisible against footage that was already compressed once by a camcorder in 2006. Where a straight copy is possible the tool takes it, and then nothing changes at all.
Why will nothing play my AVI files?
AVI is a Microsoft container from 1992 that predates modern video by a decade. It has no proper support for variable frame rates, modern codecs, or files over 4 GB, and support for it has been quietly dropped almost everywhere. Phones, smart TVs, browsers and current editing software all decline it.
My AVI has no sound after converting. Why?
Older AVI files sometimes use codecs such as AC-3 or MS ADPCM that this build cannot decode. Play the original first to confirm the sound is there. If it is, and it disappears here, the audio codec is the reason, and there is no browser-based fix for it.
Can it handle a file over 4 GB?
The tool caps out around 2 GB because the engine is a 32-bit build. That is rarely a problem with AVI in practice: the format itself struggles past 4 GB, so files of that size are uncommon and often already damaged.
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