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AVI to MP4
Convert AVI to MP4 Online — Free & Instant
Bring AVI files from old cameras and camcorders into MP4.
About AVI to MP4
AVI is a container from 1992, and it is what old camcorders, screen-capture utilities and Windows-era software left behind on a lot of hard drives. Modern phones, browsers and editors mostly will not open it. What is inside varies enormously: an AVI can hold H.264, in which case MP4 can take the stream as-is and the conversion is a millisecond-scale rewrap with no quality cost at all, or it can hold something much older — MPEG-4 Part 2, MJPEG, an ancient DivX variant — that MP4 has no clean tag for. Guessing between those two cases is how you end up with a zero-byte file and a tool that claims success, so this one reads the streams first and tells you which you have. Compatible files are copied straight over, unchanged. Incompatible ones are offered an H.264 conversion as an explicit choice, labelled for what it is: a full decode and re-encode, slow and lossy, but the only way that footage becomes portable. FFmpeg runs as WebAssembly inside your browser and the file never leaves your device.
Questions
Will my AVI convert without re-encoding?
It depends what is inside. An AVI holding H.264 can be rewrapped as MP4 in milliseconds with no quality cost at all. An AVI holding something older — MPEG-4 Part 2, MJPEG, an ancient DivX variant — has no clean MP4 equivalent, and the tool tells you that before it runs.
What happens if the codec is too old for MP4?
You are offered a conversion to H.264 as an explicit second choice, with the cost stated: every frame is decoded and encoded again, so it is slow and it is lossy. What you are not given is a silent failure or a zero-byte file, which is what a naive rewrap produces on those inputs.
Does converting to MP4 improve the picture?
No, and nothing can. A conversion can only preserve or degrade what the AVI already holds. Old camcorder footage stays old camcorder footage — it just becomes something a phone will open.
How long does it take?
A rewrap is milliseconds regardless of clip length, since no frame is decoded. An H.264 conversion is a real encode and scales with duration and resolution, so it can take minutes on a long clip; the tool estimates before you commit.
Is there a maximum AVI size?
1.5 GB, checked before the conversion starts. Old DV-format AVIs are unusually large for their running time — roughly 13 GB an hour — so long tapes may need trimming first.
Is my file uploaded to a server?
No. Transmute processes everything locally in your browser using JavaScript and WebAssembly. Your files never leave your device — there is no server, no upload, no cloud processing.