Convert AVI to MP4 without uploading anything

Where AVI files come from, and why they no longer play

AVI (Audio Video Interleave) is a Microsoft container from the early 1990s. For two decades it was everywhere: digital cameras and camcorders saved clips as AVI, Windows-era editing software exported AVI, and many movies and series downloaded in the 2000s were DivX or Xvid files in an AVI wrapper.

Today, AVI is a problem. Web browsers cannot read it at all, iPhones and most Android phones will not open it, and many smart TVs, messaging apps and upload forms reject it. The codecs inside (DivX, Xvid, Motion JPEG, MP3 or PCM audio) are just as dated as the container. Converting to MP4 with H.264 video and AAC audio makes these videos playable almost everywhere again.

How Vidmini converts AVI in your browser

Because no browser can decode AVI, Vidmini uses a built-in fallback converter: FFmpeg compiled to WebAssembly, running entirely on your device. While it works, the page shows "Preparing this format for your browser…" with a percentage. Once it is done, a notice explains that your browser could not read the format directly, so the file was converted on your device first. Vidmini then writes the final MP4.

The first time you convert an AVI, your browser downloads the 32 MB converter from vidmini.com. That download contains only program code: your video is never sent anywhere. Later conversions reuse the converter your browser already has.

Quality, speed and file size limits

An AVI to MP4 conversion is always a re-encode: the old DivX, Xvid or Motion JPEG video is turned into H.264, and the audio into AAC. Vidmini uses high-quality settings to preserve the picture as well as possible, but it is not a lossless copy. In practice, the MP4 usually looks the same as the AVI, because most AVI files were recorded at low resolutions and with modest quality to begin with.

Expect this tool to be slower than MP4 or MOV conversions. The fallback converter runs as single-threaded WebAssembly, so it cannot use your graphics hardware the way native formats can. A short camcorder clip takes seconds to a few minutes; a full-length movie can take much longer. Keep the tab open until the download button appears.

The fallback converter accepts AVI files up to 1 GB. Larger files will not work with this tool. On phones, available memory can also be a limit, so a computer is the better choice for long recordings.

Private, free and without watermark

Old AVI files are often personal: birthdays filmed on a 2005 camcorder, school plays, holiday clips. With Vidmini they stay on your device. There is no upload, no account, no watermark and no tracking cookies, and our Content Security Policy only lets the page talk to vidmini.com for its own code.

After converting, "Continue with this file" sends the MP4 to another tool, for example to compress it for sharing or trim the useless first seconds, without selecting the file again.