ASF is based on serialized objects which are essentially byte sequences identified by a GUID marker.

The different extensions are used to make it easier to identify the content of a media file.

[7] ASF files can also contain objects representing metadata, such as the artist, title, album and genre for an audio track, or the director of a video track, much like the ID3 tags of MP3 files.

Mostly, however, they contain material encoded for 'progressive download', which can be distributed by any webserver and then offers the same advantages as streaming: the file starts playing as soon as a minimum number of bytes is received and the rest of the download continues in the background while one is watching or listening.

The Library of Congress Digital Preservation project considers ASF to be the de facto successor of RIFF.