Convert AVI to MP4

Turn an old AVI into an H.264 MP4 that plays on a phone, in a browser tab, or in a messenger app.

Drop your files here

.avi, .divx · up to 300 MB

Choose files

High qualityBalancedSmall file

More settings

ResolutionHow to convertAudioAudio bitrate

How to Convert to MP4

1
Add your AVI file
Any .avi or .divx clip up to 200 MB and 5 minutes long, however old the codec inside it is.
2
Pick a quality preset
High keeps the most detail, Balanced is a good default, and Smallest file trims the size down the most for archiving.
3
Click Convert and download the MP4
The result is a standard H.264 MP4 that plays in any modern browser, on any phone, and in every messenger app.

Why you can't just rename the file

AVI is only a container, and swapping its extension to .mp4 does nothing to what is stored inside it. Most AVI files from the 2000s carry video encoded as Xvid, DivX or MJPEG, codecs no browser knows how to decode, no matter what the file is called. This tool reads that old video frame by frame with a real decoder, then re-encodes it as H.264, the one codec every browser, phone and video app understands, so the result plays without a special app or a codec pack.

Keeping audio in sync

Old AVI files are frequently written with a frame rate that drifts slightly over the length of the clip, an artifact of how early consumer video software and capture cards handled timing. Left uncorrected, that drift adds up, and by the end of a long recording the sound and picture noticeably part ways. Converting locks the whole output to one constant frame rate for its entire duration, which is exactly what keeps audio and video lined up from the first frame to the last, even on a clip several minutes long.

Converted from AVI on your device

The old AVI is read and the new MP4 written entirely inside this tab. Streams that already suit MP4 can simply be repackaged, and anything else is re-encoded by your browser's own video engine rather than a server somewhere else. Nothing is uploaded, there is no account, and closing the tab clears the clip.

Frequently asked questions

Why can't I just rename the .avi file to .mp4?

Renaming only changes the file extension, not what's encoded inside it. If the video inside is Xvid or DivX, an MP4 wrapper around it still won't play in a browser or on most phones. The video itself has to be re-encoded as H.264.

What are Xvid and DivX, and why don't they play everywhere?

They're older video codecs, popular in the 2000s for fitting a movie onto a CD or an early hard drive. They were never built into web browsers or iPhones, so files that use them need a real decoder, which this tool has, before they'll play outside a dedicated desktop player.

Why does converting an AVI take longer than some other conversions?

Because the old codec has to be fully decoded frame by frame before H.264 encoding can even start, rather than just being repackaged. A minute or two for a typical clip is normal; very long or high-resolution files take proportionally longer.

Which quality setting should I pick?

High keeps the most detail and gives the largest file; Balanced is a solid default for sharing and archiving; Smallest file trims the size the most, which suits clips you mainly want off an old drive rather than watched in top quality.

Why does the audio drift out of sync in old AVI files, and does this fix it?

Many older AVIs were recorded with a frame rate that isn't perfectly constant, so small timing errors accumulate over a long clip. Converting locks the whole video to one steady frame rate, which keeps sound and picture together from start to finish.

Will the MP4 end up smaller than the original AVI?

Usually, yes. H.264 compresses far more efficiently than Xvid or DivX at the same visual quality, so most converted files end up noticeably lighter than the source, especially at the Balanced or Smallest file setting.

What's the maximum AVI size and length this handles?

Up to 200 MB and 5 minutes for the normal conversion path, which covers the vast majority of AVI clips. Longer or heavier files can be trimmed first and converted in parts.