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Convert AVI to MP4

Convert old AVI videos from cameras, DivX and Xvid into H.264 MP4 files that play on phones and in browsers, converted in your browser.

Drop videos to convertMP4, MOV, MKV, WebM, AVI and more · up to 3 files at once free
Choose videosProcessed on your device — never uploaded
Runs in your browser · no uploadHow it works

How to use AVI to MP4

  1. 1

    Add the AVI files

    Drop up to 3 .avi videos of up to 500 MB and 10 minutes each: old camera clips, DivX or Xvid files, webcam captures.

  2. 2

    Wait for the engine the first time

    Browsers can't open AVI themselves, so a 31 MB video engine is downloaded once, with a progress bar, and cached for next time.

  3. 3

    Choose quality and size

    High is preselected; lower the resolution or pick Balanced to make big DV or MJPEG files much smaller.

  4. 4

    Convert and download

    Press Convert to MP4 and save name.mp4, which plays on phones, smart TVs and every website.

Limits and Pro

Up to 3 AVI files per batch, each up to 500 MB and 10 minutes long.

Pro converts batches of up to 500 AVI files of up to 4 GB and 10 hours each. See Pro

About AVI to MP4

AVI is Microsoft's video container from 1992, still found on old digital cameras, camcorder transfers, DivX and Xvid downloads from the 2000s, CCTV exports and some webcam software. Modern devices handle it badly: iPhones, Android galleries, Chrome and Safari can't play it, and many editors refuse it. AVI also lacks features newer formats rely on, such as reliable B-frame timing and streaming from the first byte.

No browser can read AVI on its own, so this page uses ffmpeg.wasm, the FFmpeg engine compiled to WebAssembly, which is downloaded once (31 MB) and kept in the browser cache. It opens the AVI, decodes the video — Xvid and DivX (MPEG-4 Part 2), Motion JPEG, DV, old Windows codecs — and encodes it as H.264, because copying MPEG-4 Part 2 into an MP4 would produce a file phones and browsers still can't play. MP3 sound, the usual partner of Xvid, is copied unchanged; PCM, ADPCM and AC-3 sound is converted to AAC.

This conversion runs on your processor rather than a hardware encoder, so it is slower than other conversions: roughly real time for standard-definition clips on a recent laptop, slower on phones. Interlaced camcorder footage isn't deinterlaced, so fast motion may show fine combing, as it did before. Old AVI files with damaged indexes usually still convert, but a truncated recording ends where the data stops.

Privacy

The AVI is converted by ffmpeg.wasm inside a Web Worker in this tab; the file never leaves your device. The only network request is the one-time download of the 31 MB engine from jsDelivr (or unpkg), which contains no part of your video.

AVI to MP4: frequently asked questions

Why does AVI to MP4 need a download first?
Browsers have no built-in support for the AVI container or for codecs such as Xvid, DivX and Motion JPEG. To read them, the page loads FFmpeg compiled to WebAssembly, about 31 MB, from a public CDN. It is downloaded once, with progress shown, and then cached, so later conversions start immediately. Your video itself is never sent anywhere.
Can't the video just be copied into an MP4 without re-encoding?
Technically an MP4 can hold Xvid's MPEG-4 Part 2 video, but iPhones, Android phones, Chrome, Safari and most smart TVs won't play it, which defeats the purpose. This page therefore re-encodes the picture as H.264, the codec every device supports. The MP3 soundtrack, which those devices do play inside MP4, is copied as it is.
How long does converting an AVI take?
It depends on the resolution and your device, because the conversion runs on the processor in a single thread. A standard-definition 640×480 clip converts at roughly its own playing speed on a recent laptop; HD footage and phones take several times longer. The progress bar shows the time left, and you can cancel at any moment without losing the original.
Will the MP4 be smaller than the AVI?
Usually, and often much smaller. H.264 is far more efficient than the Xvid, DivX, Motion JPEG and DV codecs in old AVI files, so the same picture quality takes less space. Camera clips in Motion JPEG or DV can shrink to a tenth of their size. Choosing Balanced or a lower resolution reduces the size further.
My AVI won't convert. What can I try?
Make sure it isn't still being copied or incomplete; a file that stops halfway converts only up to that point. Very rare codecs, such as some proprietary CCTV formats, aren't included in the browser engine and produce a clear error. Try a desktop browser if your phone runs out of memory, and keep files under 500 MB and 10 minutes on the free plan.

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