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AVI to MP4 Converter — Free, No Upload, No Watermark

Convert AVI to MP4 online: bring old AVI files up to date as MP4 that plays on phones and TVs. Free, no upload, runs in your browser.

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Drop a file here or click to browseAVI files — converted on your device, never uploaded🔒 Processed on your device — never uploaded

A video that can be copied across without re-encoding keeps its original quality, whatever you choose here.

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Convert AVI to MP4 without uploading your video

AVI is a format from the 1990s, and files like that turn up on old hard drives, camcorder cards and download folders. Phones, web browsers and most modern players no longer open them reliably. Converting to MP4 gives the same video in a format that plays almost everywhere.

What is inside an AVI

Most AVI files hold MPEG-4 video, from encoders such as DivX and Xvid, with MP3 sound. That picture format is not one that MP4 players are guaranteed to accept, so the converter re-encodes it to H.264, the format nearly every device plays, and the sound to AAC.

Quality and file size

Old AVI files were made for small screens and slow connections, so they are often low resolution. Converting cannot add detail that was never there, and re-encoding carefully avoids losing more. At Balanced quality the MP4 is usually a similar size to the AVI or a little smaller, because H.264 compresses better than the older codecs.

Before you convert

If the video is longer than you need, cut it first with the video trimmer; if it plays sideways, rotate it. For old, small clips that you want to watch on a big screen, converting does not enlarge the picture, so it will look the same as before, only playable.

How this converter works

The page reads your AVI file's header first. If the picture is H.264 and the sound is AAC or MP3, they are copied into the new MP4 without re-encoding, which takes seconds and loses nothing. Anything else is re-encoded to H.264 and AAC at the quality you choose, so the result plays everywhere.

Frequently asked questions

How do I convert AVI to MP4?
Drop your AVI file into the box above, or click to choose it, pick a quality and press Convert to MP4. When it finishes, press Download. The conversion runs in your browser, so the video stays on your device.
Is my video uploaded when I convert it?
No. The conversion runs inside your browser with a WebAssembly build of FFmpeg, and only the engine itself, about 31 MB, is downloaded, once. Your AVI file never leaves your device, and there is no watermark and no account.
Will converting AVI to MP4 reduce the quality?
Often not. If the picture inside the AVI is already H.264 with AAC or MP3 sound, it is copied into the MP4 unchanged. Otherwise it is re-encoded once, to H.264 and AAC, at the quality you choose, and the difference is hard to see at Balanced or High.
What is a AVI file?
AVI is a Microsoft container from the early 1990s. Files usually hold older MPEG-4 (DivX or Xvid) video with MP3 sound, are large for their quality, and are no longer played natively by phones or web browsers.
What is MP4?
MP4 is the most widely supported video container. It usually holds H.264 (sometimes HEVC) video with AAC sound, and it plays on practically every phone, computer, TV and browser, which makes it the safe default for sharing and uploading.
Why will my old AVI file not play on my phone?
Phones play H.264 video in MP4 or MOV, not the older MPEG-4 codecs that most AVI files use. Converting to MP4 re-encodes the picture to H.264 so the phone can play it.
Will converting AVI to MP4 make the video sharper?
No. Converting changes the format, not the detail in the picture. A small, soft AVI stays small and soft as an MP4, but it will play on devices that could not open the AVI.

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