Convert AVI to MP4

Convert AVI videos to MP4 (H.264) directly in your browser. Free and private, with no upload, no size limit and no watermark.

Drop your file here (.avi)

🔒 Private by design: your files are processed locally in your browser and never uploaded to any server.

How to convert AVI to MP4

  1. Drop your AVI file into the box above, or click to choose it.
  2. Pick a quality level — Balanced is right for most videos.
  3. Click Convert AVI to MP4, wait for the progress bar to finish, and download your MP4.

Why convert AVI to MP4?

AVI is a container format from 1992. It served the DivX era well, but today it is a compatibility headache: iPhones will not play it, most smart TVs ignore it, and web browsers cannot stream it. Old camcorder footage, downloaded clips and archived home videos are the usual suspects.

MP4 with H.264 video is the opposite: it is the closest thing to a universal video format. It plays natively on every phone, tablet, browser, TV and games console made in the last decade, and it is what every social platform expects when you upload.

This converter re-encodes your AVI into exactly that: H.264 video with AAC audio in an MP4 container, with fast-start enabled so the file can begin playing before it fully downloads.

Private and unlimited, because it runs on your device

Most online converters upload your video to their servers, which is why they cap free files at 50 or 100 MB. SysFenix runs FFmpeg — the same engine professionals use — compiled to WebAssembly inside your browser. Nothing is uploaded, so there is no size cap, no queue and no privacy question mark. Old family videos stay in the family.

The trade-off is that conversion speed depends on your device. A modern laptop converts faster than an old phone, and long videos take a while — but the progress bar keeps you posted, and the result is worth the wait.

Frequently asked questions

Is my video uploaded to a server?

No. The conversion runs entirely in your browser using a WebAssembly build of FFmpeg. Your video never leaves your device, so there is nothing to upload and nothing for anyone else to see.

Is there a file size limit?

There is no artificial limit. Because your own device does the work, you can convert files of a gigabyte or more for free — something most online converters only offer on paid plans. Very large files are limited only by your device's memory.

Why does the conversion take a while?

Video re-encoding is heavy work, and it is running on your own CPU rather than a server farm. A few minutes for a long video is normal. You can keep the tab open in the background while it works.

What settings does the MP4 use?

The output uses the H.264 video codec and AAC audio — the most compatible combination available. It plays on phones, TVs, browsers and editing software, and is optimized to start playing while it downloads.

Will there be a watermark or quality loss?

No watermark, ever. Some quality loss is inherent to re-encoding, but the default "Balanced" setting is visually indistinguishable from the original for most videos. Choose "High quality" to minimize it further.

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