By Shea Laverty

In the world of computer-viewable video, there are a wide range of various formats that can suit many different situations. Some are better suited to videos that require low file size, while others support better quality picture. Four popularly used formats are AVI, MPG, WMV and MOV. While they all serve the same purpose of storing video and audio multimedia data, these formats have a number of key differences.

Video Quality

AVI and MOV are not encoding formats, but wrappers for formatted video files. Each can contain any of a wide range of codecs that can affect video quality and compression, leading the two to possibly produce the exact same image when encoded with the same codec. WMV is designed with the ideal application being streaming over the Internet, and as a result suffers a minor loss in picture quality to minimize file size. MPEG-1, or MPG, offers the lowest quality video of these four formats.

File Size

AVI and MOV files vary in file size based on the codec used to encode the file within them. However, generally AVI tends to be larger than most video formats because of minimal compression features, once more dependent upon the codec used. MOV generally tends to be smaller, with more compression options available through different codecs. WMV and MPG both tend to be much smaller than other formats, partially due to the lowered video quality used to encode them.

Additional Features

Depending on the codecs used, an AVI file may have support for multiple video or audio streams. MOV also offers this feature, although it also has the added capability of overlaying subtitles on the main video stream if a subtitle file is available. WMV and MPG are more limited, offering little beyond the audio and video stream presented to the viewer to reduce file size.


AVI is an extremely widespread file format, supported by may video players including some mobile devices. It's one of the most commonly used formats for editing. MOV also sees widespread use, particularly among users of Apple's Mac platform, although it is slightly less common than AVI. MOV is also often a popular choice in video editing, roughly on par with AVI depending on codec use. WMV and MPG are most commonly used in online, streaming videos where the image resolution and quality are mitigated by the small file size.