What is this MP4 to AVI converter?
A free, browser-based tool that converts a MP4 video to AVI. Add a file, preview it inline, and download the result. All processing happens locally in your browser, so your video is never uploaded and there is no watermark.
AVI in 2026: only when the hardware insists
Converting MP4 to AVI is a step backward by every technical measure, and that is exactly why the valid reasons are so specific. AVI dates from 1992 and stopped evolving long before H.264 became the default; MP4 is the container the modern world standardized on. Nobody converts in this direction for quality or size. You do it because the playback side leaves no choice: industrial machines and kiosk terminals with fixed firmware, media players from the 2000s, DVD authoring suites, surveillance and signage systems that list AVI as their only input.
So treat this conversion as an adapter, not an upgrade. If the receiving device or program accepts MP4 at all, keep the MP4. Reach for AVI only when the spec sheet or the error message forces your hand.
Your MP4's codec cannot ride along
Modern MP4 files carry H.264, H.265, or AV1, and none of those sits properly in a container designed in the Windows 3.1 era. That rules out an instant rewrap: this pair means re-encoding the video, which takes real time and adds a lossy generation. Choose a high quality setting to keep that generation invisible, and budget for a similar or larger file; H.265 and AV1 sources tend to grow the most, because they pack more quality per megabyte than anything from AVI's day.
Before committing a whole batch, convert one short clip and play it on the actual target machine. Legacy decoders are picky about resolution and frame rate, and a 30-second test settles it faster than any spec sheet.
How to use it
- Add a MP4 file on the left (drag & drop or click) — it shows an inline preview.
- Pick a quality preset (used only when the video has to be re-encoded).
- Press “Convert & download” to get your AVI file. The first run downloads the ~30MB converter once.
Lossless remux vs re-encoding
MP4 and AVI are containers — what matters is the video codec inside. When the codec already fits AVI, this tool just repackages it (a "remux"): instant and completely lossless. Only when the codec isn't compatible — most often anything involving WebM — does it re-encode the video locally, which takes longer and is where the quality preset applies.