Convert AVI to MP4
From the format of a past internet to the one everything plays — converted privately on your own machine.
Drop your video or audio here
or
MP4, MOV, WebM, MKV, AVI, MP3, WAV and more — any size, no upload
🔒 Files never leave your device — everything runs in your browser.
AVI is where old memories live: camcorder transfers, early digital cameras, downloads from decades past. Modern phones, TVs, and cloud services increasingly refuse the format and its era of codecs outright. Converting to MP4 (H.264 + AAC) makes those files playable everywhere again — and usually dramatically smaller, since modern encoders achieve the same picture in a fraction of the bits.
ConvertUno ships a full software decoder for legacy formats, so even codecs your browser never heard of (DivX, Xvid, MS-MPEG4) convert right on your device. A note of honesty: a small minority of very old AVIs use proprietary codecs from defunct capture software that even it cannot decode — the tool tells you clearly instead of producing a broken file, and a desktop player like VLC remains the rescue path for those. For everything else: drop, convert, done — and nothing is uploaded, fitting for irreplaceable family footage.
How it works
- Drop your file
Any common format, any size. Nothing is uploaded — the tool runs in your browser.
- Convert
Compatible files are repackaged instantly with zero quality loss; others are hardware-transcoded at high quality.
- Download
Your converted file is ready on your device — nothing to wait for, nothing to delete from a server.
Frequently asked questions
Will converting AVI to MP4 lose quality?
The high-quality re-encode is visually faithful to the source — and since old codecs were so inefficient, the MP4 usually looks the same at a fraction of the file size. Keep the original AVI as your archive master; share the MP4.
Why does my AVI fail to convert?
A few old AVIs use proprietary codecs (early DV variants, defunct capture tools) that browsers cannot decode. The tool reports these clearly rather than guessing. VLC or HandBrake on desktop can usually still read them.
Is this safe for one-of-a-kind family videos?
Your original is never modified or uploaded — the tool only reads it and produces a new MP4 next to it on your device. The safest first step for any irreplaceable file.
Is my file uploaded to a server?
No. ConvertUno runs entirely in your browser on your own device. Your file never leaves your computer or phone — there is no upload at all.
Is it really free, with no watermark?
Yes. Processing happens on your device, so serving you costs us almost nothing — no watermark, no account, no file-size limit, no daily quota.