.avi File Extension

What kind of file is an .avi?

An .avi file is an Audio Video Interleave container created by Microsoft. It usually holds video and audio streams, but it can also contain video without audio. AVI uses the video/x-msvideo MIME type.¹

AVI is a container, not a codec. One file might contain uncompressed video and PCM audio, while another uses an older codec such as Cinepak or Indeo. Your player must understand both the AVI container and every codec inside it.

A conventional AVI begins with RIFF, a four-byte size field, and the form type AVI . In hexadecimal, the identifying pattern is 52 49 46 46 ?? ?? ?? ?? 41 56 49 20.² Checking only RIFF is not enough because WAV and WebP files use RIFF too.

How do I open an .avi on my computer?

VLC is a practical first choice on Windows, macOS, and Linux because its supported input formats include AVI and many legacy codecs.³ Windows Media Player can also play AVI when the necessary codecs are available.⁴ On macOS, IINA or VLC is generally more dependable than QuickTime Player for older AVI files. Mobile playback varies by app and by the codecs in the file.

If an AVI opens without sound, shows a blank picture, or refuses to seek, the filename may still be correct. The missing piece is often support for one contained stream. Avoid installing an unknown codec pack for a single untrusted file; try a maintained player or convert the file instead.

Poly support for .avi

Poly gives decodable AVI videos thumbnails, timeline previews, in-app playback, technical metadata, visual search, searchable speech transcripts, and agent understanding. Metadata can include duration, dimensions, frame rate, codecs, color information, and audio-track details.

Transcript search requires an audio track with audible speech. Silent videos can still benefit from visual search. A damaged AVI or one containing an unsupported legacy codec may have limited playback, indexing, or agent access.

History of .avi

Microsoft introduced AVI in 1992 as part of its Video for Windows technology. The format organizes media in RIFF chunks. Its required hdrl list describes the streams, while the movi list carries interleaved media data. A traditional idx1 chunk can provide seek locations.²

Later OpenDML extensions addressed limitations in the original structure and are often called AVI 2.0. Both original and OpenDML files normally retain the .avi suffix, so the filename alone does not reveal the version.⁵

Working with .avi and alternatives

AVI remains common in older collections, capture systems, and specialized workflows. For new web delivery, MP4 and WebM have clearer browser support.⁶

Transcoding decodes and re-encodes media, which may reduce quality. Remuxing only changes the container and preserves compatible streams exactly. Keep the original until you confirm duration, audio synchronization, frame rate, and every needed audio or subtitle stream in the new file.