Why convert AVI to MP4?
AVI (Audio Video Interleave) is a container format from the 1990s. Most modern devices have dropped support for it — iPhones won't play it at all, browsers reject it, and many smart TVs and streaming devices don't recognize it.
MP4 (H.264) is the modern standard instead. Convert once, and the file plays on every phone, tablet, browser, smart TV, and streaming platform without anyone installing extra codecs.
File size — what to expect
AVI files are often very large because older codecs like DivX, Xvid, and uncompressed video are far less efficient than H.264. Converting to H.264 MP4 typically reduces file size by 60–90% at comparable visual quality.
A 2 GB DivX AVI can commonly become a 200–400 MB MP4 at the Balanced preset with no visible quality loss. Uncompressed or MJPEG AVI files compress even more dramatically.
Supported AVI variants
Most AVI encoding variants are supported, including:
- DivX and Xvid — the most common, from early 2000s downloaded video
- MPEG-4 Part 2 — an early digital video standard
- MJPEG (Motion JPEG) — used by older cameras and capture cards
- Uncompressed AVI — very large, typically from old camcorders or screen recorders
How it works
There's no upload step — conversion starts the moment you pick the file, which is usually the slowest part of other converters. AVI's older codecs (DivX, Xvid, MJPEG, uncompressed) are decoded and re-encoded by a WebAssembly build of ffmpeg running in your browser — we only ship that code, your own CPU does the actual decoding — so speed depends on your device rather than a server queue. Nothing is uploaded — you can check that yourself in your browser's Network tab — so there's no file size cap either, and the file stays 100% private throughout, as it should.