How to convert AVI to MP4
- 1
Drop your AVI file into the converter above, or click to browse. Nothing is uploaded — the file stays on your device.
- 2
Adjust the settings (quality, resolution, and trim). Tip: Old AVI footage is often low resolution — leave resolution on “Original” and set quality to 80+ to preserve what detail is there.
- 3
Click “Convert to MP4”. The conversion runs locally in your browser — larger files take longer, and a progress bar keeps you posted.
- 4
Preview the result and hit Download to save your MP4 file.
Why convert AVI to MP4?
AVI dates back to 1992, and it shows: the container wastes space, seeks poorly, and modern devices are steadily dropping support for it and the legacy codecs it usually contains.
Converting to MP4 re-encodes with the modern H.264 codec, typically shrinking files substantially while making them playable on every current phone, browser, TV, and editor. It's the easiest way to rescue old family footage or camera archives into a future-proof format.
AVI vs MP4 at a glance
| AVI | MP4 | |
|---|---|---|
| Type | Video container (legacy) | Video container (H.264 + AAC) |
| Compression | Dated, inefficient | Lossy, very efficient |
| Audio | Yes | Yes (AAC) |
| Compatibility | Old Windows software; poor on modern devices | Universal — every device, browser, and editor |
| Best for | Legacy camera footage and archives | Sharing, social media, editing, playback anywhere |
About the formats
AVI Audio Video Interleave
AVI is Microsoft's legacy video container from 1992. It's still produced by older cameras, dashcams, and Windows tools, but it compresses poorly by modern standards and increasingly fails to open on phones, browsers, and current editing apps.
MP4 MPEG-4 Part 14
MP4 is the most widely supported video format in the world. Built on the H.264 codec with AAC audio, it plays on every phone, browser, TV, and editing app, and offers an excellent balance of quality and file size. When in doubt, MP4 is the safe choice for sharing video.
Frequently asked questions
My AVI is from an old camera — will it convert?
Almost certainly. The converter includes decoders for the codecs old cameras and Windows tools typically used (MJPEG, DivX/Xvid-era MPEG-4, and others), and re-encodes them to standard H.264 MP4.
Will the MP4 be smaller than my AVI?
Usually much smaller. AVI-era codecs are far less efficient than H.264, so at the default quality most files shrink to a fraction of their original size with no visible quality loss.
Is this AVI to MP4 converter really free?
Yes — completely free, with no watermarks, no sign-up, and no conversion limits. The tool is supported by ads on this page, so the converter itself never asks you for anything.
Are my files uploaded to a server?
No. This converter runs entirely in your browser using WebAssembly (a browser build of FFmpeg). Your AVI file never leaves your device — nothing is uploaded, stored, or seen by us, which also makes it safe for private or confidential files.
Is there a file size limit?
There's no hard limit. Because conversion happens on your own device, the practical ceiling is your browser's memory — files up to a few hundred megabytes work well on most computers. Very large files may be slow or fail on low-memory devices.
Why does the first conversion take a moment to start?
The first time you convert, your browser downloads the conversion engine (about 31 MB) once. It's cached after that, so later conversions start instantly — and they keep working even offline.
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