Convert AVI to MP4
AVI is a Microsoft video format from 1992 - a wrapper (see Codecs vs containers) that most people run into when opening old DVD rips, camcorder tapes, or downloads from the 2000s. Modern devices tolerate .avi files inconsistently: some play, some refuse, some display audio but no video. Wave converts your AVI to MP4 - copying the picture data untouched when it can, re-encoding to modern H.264 when the old codec inside won't work in MP4. The output plays on iOS, streams over Chromecast, and uploads to social platforms without complaint. Runs entirely in your browser.
What actually changes
The reason AVI conversions vary in speed comes from what's inside the wrapper. AVI can hold almost any video codec: MPEG-4 Part 2 (which you'll see called DivX or Xvid on old files - both refer to the same underlying codec), the older MPEG-2, or occasionally modern H.264. Only H.264-in-AVI can go into MP4 without re-encoding. Everything else needs a real transcode, because those older codecs technically fit inside MP4 on paper but no modern player (Chrome, Safari, iOS, Android) actually decodes them there - the file would just show a black screen. Wave decodes DivX, Xvid, and MPEG-2 sources back to raw pixels and re-encodes them to modern H.264 via WebCodecs - a browser feature that uses your device's hardware encoder - so the output plays wherever any other MP4 plays.
The bigger practical issue with AVI is that its audio and video tracks aren't strictly synchronized by design; some old files drift. Wave preserves the source timing, so if drift exists in the input it will exist in the output. If your AVI plays cleanly locally, the MP4 will too.
Microsoft introduced AVI (Audio Video Interleave) in 1992 as part of the Video for Windows initiative, back when a 640x480 video was a demanding workload. The original spec capped files at 2 GB because internal offsets used 32-bit signed integers. OpenDML, added by Matrox in 1996, extended that ceiling to effectively unlimited with a hack that hides multiple sub-2-GB "movi" chunks inside one file - which is how the DVD-rip era produced 4 GB and larger AVIs that still parse correctly in Windows Media Player and VLC today.
Audio inside AVI is usually MP3, less often AC-3 or uncompressed PCM. MP4 accepts all three; where the audio is already MP4-compatible, Wave copies it through with the video. The AVI file structure interleaves small audio and video chunks so tape-era hardware could stream from disk without seeking, which is why the format survived so long past its natural end - the interleaving still works fine on modern SSDs. AVI is also one of the formats PowerPoint deprecated in 2025 (Best video format for PowerPoint), and a common reason a TV refuses a USB stick (Why your TV won't play videos from USB).
Three steps.
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Step 1
Drop your AVI file onto the card.
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Step 2
Wave inspects the codecs and picks fast-copy or transcode automatically.
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Step 3
Convert and save.
Answers, specifically.
Why does my AVI file look old?
AVI is one of the oldest containers still in the wild. Files from 2000s-era ripping tools often use Xvid, which shows its age against modern encoders.
Can I convert without losing quality?
H.264 inside an AVI copies losslessly. DivX, Xvid and MPEG-2 AVIs need a real transcode to H.264 because no consumer browser plays those codecs inside an MP4 - Wave targets a high-quality H.264 bitrate for the re-encode, and on typical live-action content the visible loss is negligible against the source's own DivX / Xvid compression.
Why do modern apps refuse AVIs?
Streaming platforms and mobile OSes standardized on MP4 and HEVC. AVI's variable-block structure doesn't fit their pipelines.
What happens to subtitle tracks?
AVIs rarely carry proper subtitle tracks. When they do (MicroDVD-style), Wave drops them - MP4 subtitle mux support in the current build is limited.
Are there size limits?
About 1.5 GB comfortably. Most AVIs from the era are well under this.
How can I tell if my AVI is DivX or Xvid?
Wave shows the FourCC on the inspect screen. DIVX, DX50, and DIV3 are DivX; XVID is Xvid. Practically, they behave identically inside AVI - both are MPEG-4 Part 2 ASP, and Wave transcodes both to H.264 for the MP4 output.
My AVI has a 2 GB size and no metadata past halfway. Bug in Wave?
That is the classic pre-OpenDML AVI size cap. The file itself is truncated at 2 GB - Wave will convert what is there, but everything past the 2 GB mark is gone from the source. If you have an original copy, re-rip with a tool that emits OpenDML AVIs or MKV.
What about multi-language AVIs with separate audio tracks?
Rare in AVI but they exist. Wave picks the first audio stream in the container; secondary tracks are dropped. Multi-track passthrough in the MP4 output is on the roadmap.