Free online MP4 to AVI converter

Some older video editors, playback devices, and production systems accept AVI but reject MP4. Converting the file changes its container and may also require re-encoding the video or audio for compatibility.

What the MP4 format is

MP4 is a multimedia container based on the ISO Base Media File Format. It commonly stores H.264 or H.265 video with AAC audio, but it can also contain other codecs, subtitles, metadata, and multiple streams.

Phones, cameras, screen-recording applications, streaming tools, and editing programs frequently create MP4 files. Modern operating systems, browsers, televisions, and video editors generally support MP4 because it combines efficient compression with broad codec support.

What the AVI format is

AVI, or Audio Video Interleave, is a Microsoft RIFF container introduced for Windows video. It can hold different video and audio codecs, including MPEG-4 Part 2, Motion JPEG, uncompressed video, and PCM audio.

AVI is still used by older Windows software, legacy capture hardware, some industrial systems, and applications that specifically require the .avi extension. Its relatively simple structure can help with legacy compatibility, but AVI usually compresses less efficiently than MP4 and has weaker support for variable frame rates, chapters, modern subtitles, HDR metadata, and some multichannel audio layouts.

How to convert the file

For a single file without installing software, use the converter on 101convert.com: upload the MP4, choose AVI as the output format, start the conversion, and download the resulting file. Do not upload confidential footage unless the service's storage and deletion terms are acceptable.

For local processing, FFmpeg provides control over codecs, quality, scaling, and batch conversion. Open a terminal in the folder containing the source file and run:

ffmpeg -i input.mp4 -c:v mpeg4 -q:v 4 -c:a libmp3lame -b:a 192k output.avi

This encodes video as MPEG-4 Part 2 and audio as MP3, a combination accepted by many older AVI applications. Replace input.mp4 and output.avi with the actual filenames. FFmpeg builds without the MP3 encoder may require a different installed audio encoder.

The command keeps the source dimensions and frame rate unless you specify other options. To reduce resolution while preserving the aspect ratio, add a scale filter:

ffmpeg -i input.mp4 -vf scale=1280:-2 -c:v mpeg4 -q:v 5 -c:a libmp3lame -b:a 160k output.avi

The -2 calculates an even output height. With FFmpeg's MPEG-4 encoder, a lower -q:v value normally gives higher quality and a larger file; test the result in the target application before applying the setting to a batch.

Desktop applications such as VLC, HandBrake, and dedicated video editors can also perform conversions, but their AVI codec choices and compatibility presets vary. Check the destination system's required video and audio codecs rather than selecting AVI based only on the filename extension.

Quality and compatibility limits

Changing the container alone does not improve quality. If the destination codecs differ from the source codecs, the video and audio are decoded and re-encoded, causing generation loss. An AVI file can therefore look worse than the original MP4 even when its resolution and frame rate are unchanged.

AVI output is often much larger because MPEG-4 Part 2, Motion JPEG, or uncompressed video is generally less efficient than H.264 or H.265. Older AVI software may also impose 2 GB or 4 GB file-size limits, although OpenDML AVI supports larger files.

Stream copying avoids re-encoding when the existing streams are compatible with AVI:

ffmpeg -i input.mp4 -c copy output.avi

This is not a universal conversion. H.264 video or AAC audio copied from MP4 may cause playback, seeking, or synchronization problems because the destination application may not support those streams in an AVI container. Re-encoding to MPEG-4 Part 2 and MP3 is usually safer for legacy software. Test the converted file on the exact device or program that requires AVI.