Convert AVI to MP4
Convert AVI videos to modern MP4 with H.264. Reduce file size up to 80%. Free, in your browser, no file uploads.
.avi · up to 100 MB
Why convert AVI to MP4
Modernize your legacy Windows videos
Universal compatibility
From legacy Windows format to MP4: compatible with any platform, player, and social network.
Guaranteed privacy
Your video never leaves your device. Local conversion with FFmpeg.wasm, no uploads.
Massive size reduction
H.264 can reduce a 1 GB AVI to 100-200 MB with equivalent visual quality.
No software to install
No need for HandBrake, VLC, or any program. Everything runs in the browser, nothing to install.
How it works
Three steps, no hassle
Select your AVI video
Drag or select your .avi file — whether from an old camera, screen recording software, or classic video archive.
H.264 re-encoding locally
FFmpeg.wasm re-encodes the video with H.264 and audio with AAC, drastically reducing file size without visible quality loss. Your file is never uploaded to any server.
Download your optimized MP4
The resulting MP4 is up to 5-10x smaller than the original AVI and compatible with any device or platform.
FAQ
Got questions?
AVI (Audio Video Interleave) was designed by Microsoft in 1992, when storage was expensive but processing power was limited. To simplify playback, AVI files typically use codecs with minimal compression or even uncompressed video. AVI also does not natively support modern features like multiple audio tracks, subtitles, or advanced metadata. The result is files 5-10x larger than an equivalent MP4 with H.264.
The reduction depends on the original AVI codec. An uncompressed or old DivX/Xvid AVI can shrink from 1 GB to 100-200 MB with H.264, an 80-90% reduction. If the AVI already uses H.264 internally (some do), the reduction will be smaller since you are re-encoding already compressed data. In any case, the resulting MP4 will take considerably less space.
Technically yes, since H.264 is a lossy codec. However, H.264 is significantly more efficient than typical AVI codecs (DivX, Xvid, MPEG-2). With CRF 23 (default), the visual difference is practically imperceptible for most content. For files that are already heavily compressed, re-encoding may introduce somewhat more degradation.
AVI remains in specific niches: old security cameras and DVRs, legacy screen capture software (some older versions of Fraps, Camtasia), mid-to-low-range digital cameras manufactured before 2012, and historical archive files. If you have a collection of family videos recorded before 2010, many of them are probably in AVI.
Time is proportional to file size and device performance. A 500 MB AVI can take 3-10 minutes on a modern computer. AVI files tend to be large, so patience is needed. The first conversion also includes downloading the FFmpeg engine (~25 MB), which is cached for later use.
The tool works best in Chrome and Edge (Chromium), which have the best WebAssembly implementation. Firefox also works but may have some limitations with ffmpeg.wasm for very large files. Safari on macOS works but with stricter memory restrictions. Chrome or Edge is recommended for the best experience.
AVI to MP4: AVI format history (Microsoft 1992), the codec evolution from DivX/Xvid to H.264, and the container format wars
AVI (Audio Video Interleave) was introduced by Microsoft in November 1992 as part of the Video for Windows software package, designed to enable video playback on personal computers running Windows 3.1. At the time, playing video on a PC was a technical achievement: processors could barely decompress video in real time. AVI solved this with an 'interleave' design: alternating blocks of video frames and audio samples in the file to minimize hard disk reads, which was the main bottleneck.
The great AVI crisis came in the late 1990s with the rise of pirated video and the first DVD rips. The DivX codec (originally an illegal hack of Microsoft MPEG-4 v3) and Xvid (the open-source version) made it possible to compress full movies into 700 MB for a CD. These files were technically AVI with a DivX/Xvid codec inside — a brilliant solution but fraught with compatibility problems. The transition to H.264 (published in 2003, widely adopted from 2005 onwards) was gradual but inevitable: H.264 offered twice the compression efficiency of DivX with better visual quality.
Today, the video codec ecosystem has evolved toward H.265/HEVC (2013, double H.264 efficiency), VP9 (Google, 2013, YouTube standard), and AV1 (Alliance for Open Media, 2018, royalty-free, 30% more efficient than H.265). However, H.264 inside an MP4 container remains the universal common denominator: supported by 100% of modern devices, browsers, streaming platforms, and social networks. Converting your AVI to MP4/H.264 guarantees your videos will work on any device for decades to come.