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AVI to MP4

Details

How to use AVI to MP4

What the tool does, how to run it, and what to expect from the result.

How to convert an old AVI to MP4

This page loads a WebAssembly build of ffmpeg into your browser, decodes whatever codec the AVI is carrying, and re-encodes it as H.264 video with AAC audio in an MP4 container. Nothing is uploaded.

Treat the result as a compatibility copy, not an upgrade. Keep the AVI if it is the only copy you have, because the MP4 has been through one more lossy generation than the source and there is no way back.

  • Drop the AVI onto the upload area and wait for the duration and resolution to appear.
  • Compare the reported dimensions against how the clip actually looks; a mismatch is the usual anamorphic aspect ratio trap.
  • Pick Balanced (CRF 27) unless you specifically need a smaller file.
  • Run the conversion, leaving the tab open until it finishes.
  • Download the MP4, watch the first few seconds, and keep the original AVI as your archive copy.

Why a generic app launch draft can be more useful here

Alternative app stores and third-party marketplaces often have less standardized promo workflows. In practice, teams just need a clean, reusable short video draft from screenshots.

This page keeps the defaults generic on purpose, so the same local builder can adapt to different store surfaces without pretending to be an official platform tool.

What this page should help with

It is useful for launch drafts, screenshot storyboards, and short promo videos built from screenshots when the publishing destination is more flexible or mixed.

  • Generic app launch promo drafts
  • Alternative Android store visuals
  • Third-party marketplace screenshot videos
  • Local browser preview and export with no server rendering
Tips

Getting a better result out of AVI to MP4

Specific settings and thresholds, not general advice.

  • AVI is a container from 1992 and the video inside it is almost always already lossy, usually Xvid or DivX (MPEG-4 Part 2) or Motion JPEG. Re-encoding to H.264 at CRF 27 stacks a second generation of loss on top of the first, so an old AVI will never look better after conversion, only more compatible.
  • The re-encode is done by ffmpeg compiled to WebAssembly, with libx264 at preset veryfast, CRF 27 on Balanced, 31 on Smaller file, and 35 on Aggressive, plus AAC audio at 128 kbps.
  • Motion JPEG AVI files, the kind old digital cameras and dashcams wrote, are enormous for their quality because every frame is a standalone JPEG with no motion compensation. These are the AVIs where converting to MP4 genuinely shrinks the file, often by 80% or more.
  • AVI has no clean way to signal a non-square pixel aspect ratio, so anamorphic AVIs can come out looking horizontally stretched or squeezed. Check the first frame of the output before you throw the source away.
  • If the AVI is an old encode you care about, keep the original file after converting. The MP4 is a delivery copy and there is no path back to the source quality from it.
Limits

What AVI to MP4 does not do

The honest boundary, so you do not lose time finding it yourself.

  • Only the first video track and one audio track are carried over. Any second audio track and any external-style embedded data is dropped.
  • There is no stream copy path. AVI codecs are not MP4-legal, so decoding and re-encoding is unavoidable here regardless of the tool.
  • Output is 8-bit H.264 in 4:2:0 only. No 10-bit, no HEVC, no AV1.
  • The encoder is single-threaded WebAssembly inside your tab, so a full-length AVI is a poor fit; short clips convert comfortably, hour-long files often will not.
Reference

Terms used on this page

Short, plain-language definitions for the formats and settings above.

Files & formatsCodecA codec is the method used to compress and decompress video or audio — it decides how much detail is kept and how small the file becomes. Common video codecs are H.264 and HEVC (H.265); common audio codecs are AAC and MP3. The codec, not the file extension, controls quality and size.GeneralPhotos & videoScreenshotA screenshot is an image captured of whatever is on your screen, saved into your photo library like a regular picture. Individually small, screenshots accumulate fast and clutter the camera roll because most are saved once and never needed again.iOSAndroidGeneral
At a glance

Who AVI to MP4 is for

A quick way to understand who this helps, what it solves, and where it connects next.

Best fit

People with legacy AVI files that will not play or upload on current devices

Ideal for

Modernizing an old AVI clip into a compact, widely supported MP4

FAQ

Common questions

Short answers for the questions people usually have before trying a utility like this.

Is this tied to one store?

No. This page is intentionally generic and is meant for alternative Android stores or third-party app marketplaces that do not fit a more specific store flow.

Can I still switch the canvas and pacing?

Yes. The page opens with a generic app launch setup, but the same arrange, canvas, pacing, and export controls remain available.

Does export remain local-only?

Yes. Preview and export stay on the device in the browser, without server-side video rendering.

Will the MP4 look better than the AVI?

No. Re-encoding cannot add back detail that the original codec already threw away, and it removes a little more of its own. What you gain is playability on phones, browsers, and modern editors, which is the only reason to convert.

Why did my AVI get much smaller?

If it was Motion JPEG, every frame was stored as a separate JPEG with no compression between frames. H.264 exploits the similarity between consecutive frames, which is why the MP4 can be a fraction of the size at the same apparent quality.

The output looks stretched. What happened?

AVI handles non-square pixel aspect ratios poorly, so an anamorphic source can be misread. Compare a frame from the source against the output and, if the geometry is wrong, use a desktop tool where you can set the aspect ratio explicitly.

Is there a size limit on the AVI I can drop in?

There is no hard limit in the page, but the whole file is handled inside your tab's memory by a WebAssembly encoder. Large files will be slow and very large ones can run out of memory and fail.

Does the file leave my device?

No. The AVI is decoded and re-encoded locally. The only network request is for the encoder's WebAssembly binary, fetched from a public CDN the first time you convert.

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