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How to Convert AVI to MP4 (Old Camera Videos)

Turn old AVI videos from digital cameras and camcorders into MP4 that plays on phones, TVs and in browsers, often much smaller too. Try it with a free account.

Published · 5 min read

To convert AVI to MP4, re-encode the video as H.264 inside an MP4 file, the format every phone, TV and browser plays. Our MOV to MP4 converter takes AVI files too: choose the file, press Start, and download an MP4. Old camera AVIs often come out much smaller as a bonus. It's a pro tool you can try with a free account on videos up to 30 seconds. One big catch: your browser has to be able to read the AVI's length first, and with most AVIs it can't, so the page may refuse the file (more on that below).

Why AVI files cause trouble now

AVI is a Microsoft format from the early 1990s. It was everywhere in the 2000s: compact digital cameras recorded their video clips as AVI, and so did many camcorders, webcams and old phones. The problem is what's inside:

  • Old codecs. Many camera AVIs use Motion JPEG, which stores every frame as a separate photo. Others use DivX, Xvid or other early formats. Phones, smart TVs, browsers and modern editing apps often don't support them.
  • Huge files for their quality. Motion JPEG is very inefficient by today's standards, so a few minutes of standard-definition video can be hundreds of megabytes.

MP4 with H.264 video and AAC sound fixes both: it plays almost everywhere and is far more efficient.

Step by step

  1. Open the MOV to MP4 converter and sign in.
  2. Under Choose a file, pick your AVI, up to 1 GB and 30 minutes.
  3. The page reads the video's length in your browser to check it against your allowance. If it can, you'll see Start; press it.
  4. Wait while it converts.
  5. Press Download result to save your MP4. It's kept for 1 hour.

There are no settings to choose. For a batch of old clips, convert them one at a time.

If you see "We couldn't read that file"

Before anything is uploaded, the page asks your browser for the video's length. Browsers play MP4 and WebM but generally can't open AVI files, so with many AVIs the check fails with "We couldn't read that file." Nothing is uploaded and no free try is used.

If that happens, you have two practical choices:

  • Convert it on your computer. A free desktop media player with a conversion feature, such as VLC (Media > Convert / Save), can turn AVI into MP4 offline. Choose an H.264 + MP3 or AAC MP4 profile.
  • Check the camera's software. Some cameras came with software that exports clips as MP4.

We're telling you this up front because most AVI files hit this check. AVIs that browsers can read convert normally.

What happens to the quality and size

The converter checks the video inside the AVI:

  • Old codecs (Motion JPEG, DivX, Xvid and others) are re-encoded as H.264 at high quality. Because H.264 is so much more efficient, the MP4 is often a fraction of the AVI's size and looks the same.
  • H.264 already (some later cameras used it inside AVI): if the file isn't unusually large for its length, the video is moved into an MP4 without re-encoding, so the picture doesn't change at all.

Sound in formats that MP4 doesn't usually carry, such as the PCM audio many cameras recorded, is converted to AAC, the standard MP4 sound. Old standard-definition clips (like 640 × 480) keep their size; nothing is enlarged. Anything above 1080p is scaled down to 1080p, which is rare for AVI.

Tips for old family videos

  • Keep the originals. Store the AVIs alongside the MP4s until you're sure the conversion is good.
  • Don't expect HD. A 640 × 480 clip from 2005 will look like a 640 × 480 clip on a big TV. Conversion fixes playback, not resolution.
  • Sideways clips were common on cameras that didn't record rotation. Fix them after converting with rotate video (a pro tool; a free account can try it on a video up to 30 seconds) or a video editor.
  • Need it smaller still for WhatsApp or email? Run the MP4 through the video compressor. See how to compress a video for WhatsApp and email.
  • Old photos from the same camera may need help too: see restore old family photos.

For other formats, see how to convert MKV to MP4, WebM to MP4 and MOV to MP4. Our explainer on what a video codec is explains why the format inside the file matters more than the file extension.

Trying it free

MOV to MP4 is a pro tool. A free account can try it on videos up to 30 seconds, and you get 5 free tries a day across all our pro tools. Many old camera clips are that short. Longer videos, up to 30 minutes and 1 GB, need a paid plan.

Your files and privacy

Conversion runs on our servers, so your video is uploaded. It's deleted as soon as it's converted, and your MP4 is available to download for 1 hour, then deleted too.

Convert your AVI

Choose your AVI in the MOV to MP4 converter, press Start and download an MP4 that plays anywhere. Clips up to 30 seconds can be tried with a free account.

Will converting AVI to MP4 lose quality?
If the AVI is re-encoded, a tiny amount, at a level that's very hard to see. If it already contains H.264, the video is repackaged without any change.
Why is my MP4 so much smaller than the AVI?
Old cameras used inefficient formats like Motion JPEG. H.264 stores the same picture in far less space.
Why does the page say it couldn't read my AVI?
Your browser can't open that AVI to check its length, which happens with most AVI files. Convert it offline with a desktop media player instead.
Can I convert several AVI files at once?
Not in one go. Convert them one at a time, each up to 1 GB and 30 minutes.
Will the MP4 play on my TV and phone?
Yes. MP4 with H.264 video and AAC sound plays on almost every smart TV, phone, computer and browser.

Video tools

Try MOV to MP4

Free to try with a free account. Convert MOV, MKV, WEBM and other videos to MP4, the format that plays on almost every phone, computer and website.

Open MOV to MP4

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