What is a .avi file?
Audio Video Interleave · Video · Microsoft · 1992
AVI is an old Microsoft video container that you still meet in legacy files and some cameras. It is widely playable but inefficient by modern standards, so large AVIs are usually converted to MP4 to save space.
What is a .avi file used for?
AVI was Windows' standard video format for years. It interleaves audio and video chunks in a simple structure that many programs can read.
By today's measures it is bulky, lacks modern features like proper streaming and soft subtitles, and its files are larger than an equivalent MP4.
Like any container, an AVI holds whatever codec was used inside it, often older ones such as DivX or Xvid. That is why an AVI sometimes plays with picture but no sound, or refuses to open at all: the player is missing that codec. VLC, which bundles its own, is the reliable fix.
The size difference with modern formats is stark. An AVI using an old codec can be several times larger than the same footage encoded as H.264 in an MP4, with no visible gain in quality. If storage or upload limits matter, re-encoding to MP4 is almost always worth it. HandBrake is the usual free tool: load the AVI, pick the MP4 preset, and it shrinks the file while keeping the picture.
AVI also lacks features people now take for granted. It has no native support for soft (switchable) subtitles, chapters or multiple selectable audio tracks the way MKV and MP4 do, and it does not stream smoothly over the web. For editing, most modern editors accept AVI but prefer MP4 or MOV, so converting first avoids codec headaches on the timeline.
VLC plays AVI reliably on every platform. When size, streaming or compatibility matters, convert it to MP4.
What opens a .avi file?
The .avi format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list.
Windows
- Media Player
- VLC
macOS
- VLC
- QuickTime (with codecs)
Linux
- VLC
- mpv
Web
- Not natively, convert first
Open a .avi file step by step
- Confirm the file really is a .avi. Drop it into the WhatFileType identifier, which reads its signature in your browser without uploading anything.
- On Windows, open it with Media Player or VLC.
- On Mac, use VLC or QuickTime (with codecs).
- On Linux, try VLC or mpv.
- Still stuck? Convert the .avi to MP4, which opens more widely.
Why can't I open my .avi file?
Almost always because no installed app understands AVI. Install one of the apps above, or convert the file to a format your existing software already reads. If double-clicking opens the wrong program instead of nothing at all, the file association is set to the wrong app rather than the file being broken.
The other possibility is that the file is not really a .avi at all. Drop it into the file identifier to check it by its bytes instead of its name. Nothing is uploaded.
How to convert a .avi file
You can convert a .avi file to MP4, MKV, WebM.
HandBrake and FFmpeg both convert AVI to MP4. FFmpeg can often do it without re-encoding at all when the streams are already compatible: ffmpeg -i in.avi -c copy out.mp4. That is instant and lossless.
What is the .avi file signature (magic bytes)?
A .avi file starts with the hex bytes 52 49 46 46 ?? ?? ?? ?? 41 56 49 20, which read as RIFF....AVI in ASCII. Programs identify AVI by those bytes, not by the filename, so a renamed file still gives itself away.
These are the documented signatures for AVI. For a full breakdown, see the AVI file signature page.
| Hex signature | Offset | ASCII | Note |
|---|---|---|---|
| 52 49 46 46 ?? ?? ?? ?? 41 56 49 20 | 0 | RIFF....AVI | RIFF....AVI |
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .avi file?
AVI is an old Microsoft video container that you still meet in legacy files and some cameras. It is widely playable but inefficient by modern standards, so large AVIs are usually converted to MP4 to save space.
Why won't my AVI play, or why is there no sound?
Almost always a missing codec. The AVI container is fine, but the video or audio codec inside (often DivX or Xvid) is not installed on your system. Open the file in VLC, which includes its own codecs, or convert it to MP4.
Should I convert AVI to MP4?
Usually yes. MP4 is smaller, plays on more devices and browsers, and keeps similar quality.
How do I make an AVI file smaller?
Re-encode it to MP4 with H.264. In HandBrake, load the AVI, choose an MP4 preset and export. The same footage often ends up a fraction of the size with no visible quality loss.
How do I play an AVI on a phone or in a browser?
Phones and browsers rarely play AVI directly. Convert it to MP4 first, which iPhones, Android and every browser support, or use the VLC mobile app.
Comparisons
Related formats
Sources
Details on this page were checked against authoritative references. How sources are ranked and what is deliberately left out is set out in the methodology.