Is my file uploaded anywhere?

No. Your file is read and processed inside this browser tab and never leaves your device. You can confirm it in your browser's developer tools: the Network tab shows no upload.

Does converting MP4 to AVI reduce quality?

The video is re-encoded as H.264 at CRF 23 (ffmpeg's default quality level, "veryfast" preset) with AAC audio. That looks very close to the source for most footage, but it is a lossy re-encode, so fine detail and grain can soften slightly.

Is there a file size limit?

Yes: 500MB per file. There's no account and no limit on how many files you convert.

What's the difference between MP4 and AVI?

MP4 (MPEG-4 Part 14) and AVI (Audio Video Interleave) store data differently. MP4: lossy (H.264/H.265 video, AAC audio). AVI: varies (codec-dependent; often uncompressed or lightly compressed). AVI is a Microsoft container format dating to 1992 — still turns up in older camcorder footage and legacy software exports, but obsolete for modern delivery.

Why convert MP4 to AVI?

Common uses for AVI: Playing back old camcorder or capture-card footage; Legacy CCTV/DVR exports; Archived software-generated video. Extremely simple, well-documented container structure with minimal parsing overhead for old hardware and software.

What MIME type does a .avi file use?

video/x-msvideo, the standard type for Audio Video Interleave.

What is the ffmpeg command to convert MP4 to AVI?

Run: ffmpeg -i input.mp4 -c:v libx264 -preset veryfast -crf 23 -c:a aac output.avi. This is the exact command FreePrivateConvert runs for this conversion, so you can use this page instead of installing ffmpeg: it runs the same conversion inside your browser.

Convert MP4 to AVI

To convert MP4 to AVI, add your .mp4 file below and press the button: it's processed on your own device and you download the result, with nothing uploaded. It's free, needs no account, and works with files up to 500MB.

Drop a .mp4 file or click to browse

Max file size 500MB • No Account Required • Files Never Touch a Server

File signature verified before conversion — never uploaded

About converting MP4 to AVI

MP4 (.mp4) files can be converted to AVI entirely in your browser — no software to install, no file upload, and no account required. The conversion runs on a WebAssembly build of ffmpeg directly on your device.

Technical comparison

	MP4	AVI
Category	video	video
Compression type	Lossy (H.264/H.265 video, AAC audio)	Varies (codec-dependent; often uncompressed or lightly compressed)
Typical file size	Moderate — a few MB per minute of 1080p video, varying with CRF/bitrate	Large — often stores uncompressed or lightly-compressed video
Transparency support	No	No

How to convert MP4 to AVI privately

Every step below runs on a WebAssembly build of ffmpeg inside this browser tab. Your .mp4 file is never uploaded to a server — there's no network request carrying it anywhere.

Add your MP4 file
Drag and drop, or click to select, a file (.mp4). It's read straight from disk into browser memory — no upload step exists.
Convert locally
FreePrivateConvert converts it to AVI using a WebAssembly build of ffmpeg, entirely within this browser tab.
Download the result
Save your converted .avi file. It only ever existed in this tab's memory — closing the tab without downloading discards it completely.

Convert MP4 to AVI with ffmpeg (command line)

Prefer the terminal? This is the exact ffmpeg command this page runs for you:

ffmpeg -i input.mp4 -c:v libx264 -preset veryfast -crf 23 -c:a aac output.avi

-i input.mp4: Your MP4 file.
-c:v libx264: Encode the video as H.264, the format virtually every phone, browser and TV plays.
-preset veryfast: Encoding speed vs. file size trade-off: veryfast encodes quickly with a slightly larger file.
-crf 23: Constant quality level (lower = better quality and bigger file; 18-28 is the usual range, 23 is the default).
-c:a aac: Encode the audio as AAC.
output.avi: The AVI file to create. ffmpeg picks the container from this extension.

Don't have ffmpeg installed? You don't need it: use the converter at the top of this page. It runs the same conversion on your own device, and your file is never uploaded.

FAQ

Is my file uploaded anywhere?: No. Your file is read and processed inside this browser tab and never leaves your device. You can confirm it in your browser's developer tools: the Network tab shows no upload.
Does converting MP4 to AVI reduce quality?: The video is re-encoded as H.264 at CRF 23 (ffmpeg's default quality level, "veryfast" preset) with AAC audio. That looks very close to the source for most footage, but it is a lossy re-encode, so fine detail and grain can soften slightly.
Is there a file size limit?: Yes: 500MB per file. There's no account and no limit on how many files you convert.
What's the difference between MP4 and AVI?: MP4 (MPEG-4 Part 14) and AVI (Audio Video Interleave) store data differently. MP4: lossy (H.264/H.265 video, AAC audio). AVI: varies (codec-dependent; often uncompressed or lightly compressed). AVI is a Microsoft container format dating to 1992 — still turns up in older camcorder footage and legacy software exports, but obsolete for modern delivery.
Why convert MP4 to AVI?: Common uses for AVI: Playing back old camcorder or capture-card footage; Legacy CCTV/DVR exports; Archived software-generated video. Extremely simple, well-documented container structure with minimal parsing overhead for old hardware and software.
What MIME type does a .avi file use?: video/x-msvideo, the standard type for Audio Video Interleave.
What is the ffmpeg command to convert MP4 to AVI?: Run: ffmpeg -i input.mp4 -c:v libx264 -preset veryfast -crf 23 -c:a aac output.avi. This is the exact command FreePrivateConvert runs for this conversion, so you can use this page instead of installing ffmpeg: it runs the same conversion inside your browser.

Last updated 26 September 2026

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