How to convert AVI to MP4 online
- 1
Drop your AVI file
Drag and drop your Audio Video Interleave file onto the converter, or click to browse your files. You can select up to 5 at once. Nothing leaves your device — conversion happens right here in the browser.
- 2
Hit Convert — it happens locally
Click Convert and watch it go. There's no upload, no server queue, no waiting. The converter runs Audio Video Interleave → MPEG-4 Part 14 entirely in your browser tab. Most files finish in 1–3 seconds.
- 3
Download your MP4
Your MPEG-4 Part 14 file is ready. Click Download, or grab a ZIP if you converted a batch. Close the tab and everything disappears — no copies kept anywhere.
AVI vs MP4: format overview
Audio Video Interleave
Microsoft · 1992
- Compression
- lossy
- Transparency
- No
- ✓ Universal Windows compatibility
- ✓ Simple container format — widely supported
- ✗ Large file sizes (minimal compression)
MPEG-4 Part 14
Moving Picture Experts Group · 2001
- Compression
- lossy
- Transparency
- No
- ✓ Universal compatibility across all platforms
- ✓ Excellent compression with H.264/H.265
AVI magic bytes: 52 49 46 46 xx xx xx xx 41 56 49 20
MP4 magic bytes: 00 00 00 xx 66 74 79 70
Why convert AVI to MP4?
AVI is a Microsoft container format from 1992 that became the default output of consumer DV cameras and early DVD ripping software throughout the 1990s and 2000s. Those files are still sitting on hard drives and external disks in enormous numbers. The format has no built-in streaming support, no chapter metadata, and was commonly encoded with DivX or XviZ codecs that require separate codec packs on modern systems. iOS and Android will outright refuse to play many AVI files, and web browsers cannot embed them.
MP4 with H.264 video is the current universal standard. Every phone, every browser, every smart TV, every social platform, and every video editor accepts it without configuration. H.264 MP4 also compresses dramatically better than the older AVI codecs — you can expect the converted file to be 50 to 75 percent smaller than the original AVI at equivalent visual quality. That matters when you are uploading home videos to Google Photos, sending clips via WhatsApp, or sharing footage from an old camcorder with family members.
Conversion from AVI to MP4 H.264 is lossless in terms of visible quality degradation at standard settings — the encoder simply repackages and recompresses the video more efficiently. If the source AVI was captured at high resolution, the MP4 will preserve it. Files with unusual DivX or XviZ encoding from the early 2000s occasionally produce audio sync issues after conversion; if you notice this, try re-encoding with a fixed audio offset or use the original file's audio track directly.
Quality & file size: AVI to MP4
Typical file sizes: AVI 200–600 MB → MP4 100–300 MB.
Both AVI and MP4 use lossy compression. We transcode at high quality settings (equivalent to MP4's recommended web quality) to minimize generational loss.
Color depth: AVI supports standard color, MP4 supports standard color.
Transparency: AVI does not support transparency. MP4 does not support transparency — transparent areas become solid white.
Frequently asked questions
Privacy: how FormatDrop handles your files
Your AVI files are converted 100% inside your browser. They are never uploaded to our servers, never stored, and never seen by anyone other than you. This isn't a privacy policy claim — it's an architectural guarantee: our server has no endpoint that receives file bytes.