MP4 (MPEG-4 Part 14) and AVI (Audio Video Interleave) are built for different jobs. MP4 is typically used for sharing, social media, streaming, while AVI is best for older players and software. Converting lets you open, share or upload your files wherever AVI is expected.
How to use the MP4 to AVI converter
- Add your MP4 filesClick “Choose Files” or drag and drop them into the box. You can add many files at once — or paste a file with Ctrl+V.
- Choose AVI and adjust settingsAVI is selected automatically. Optionally open Settings to change resolution, quality or frame rate.
- Convert and downloadPress “Convert”. Your AVI files appear instantly — download them one by one or all together as a ZIP.
MP4 vs AVI
MP4 MPEG-4 Part 14
MP4 is the most compatible video format in the world. It plays on iPhones, Android, Windows, Mac, smart TVs and every browser, and is accepted by YouTube, Instagram, TikTok and WhatsApp.
- Compression
- Lossy (H.264/H.265)
- Features
- Video, audio, subtitles
- Origin
- 2001, MPEG
- Best for
- Sharing, social media, streaming
AVI Audio Video Interleave
AVI is one of the oldest Windows video containers. It is widely supported by legacy players, DVD players and older software, but files are larger than modern MP4 at the same quality.
- Compression
- Varies (DivX/Xvid/MJPEG)
- Features
- Video + audio
- Origin
- 1992, Microsoft
- Best for
- Older players and software
Why use ConvertMathly?
Files are processed on your device and never uploaded. Close the tab and they are gone.
No account, no daily cap, no queue and no watermark — convert as much as you want.
The same engine used by professional video tools, running in your browser via WebAssembly.
Windows, Mac, Linux, Chromebook, iPhone and Android — any modern browser, nothing to install.
Frequently asked questions
How do I convert MP4 to AVI?
Add your MP4 files above, make sure AVI is selected and press Convert. The AVI files are ready to download a few seconds later — no installation or account required.
Why does the first conversion take a little longer?
The video engine (FFmpeg compiled to WebAssembly, about 30 MB) is downloaded once and then cached by your browser. After that, conversions start immediately — even offline.
Is there a file size limit?
There is no artificial limit. Because the conversion runs in your browser, the practical limit is your device memory — files up to around 1–2 GB work on most computers. Long videos take longer on phones.
Are my MP4 files uploaded to a server?
No. ConvertMathly converts files entirely inside your web browser using JavaScript and WebAssembly. Your files never leave your computer or phone, which makes it safe for private photos and documents.
Can I convert multiple MP4 files at once?
Yes — add as many files as you like. They are converted one after another and you can download everything in a single ZIP.