Octet StreamAn octet stream is an unordered series of bytes. The term is used as the default designation for binary files received within the context of hypertext transfer protocol.
Every document returned by a server is tagged with a header indicating the nature of the file. Client browsers use that header to determine how to display the document. If the client program cannot recognize the file extension listed in content header, it checks to see if the file is binary. If so, the files is designated as "application/octet-stream," and the user is prompted to save the file rather than read it to the screen as text. The Netscape browser assigns .exe. and .bin files as application/octet-stream by default; Mosaic does the same for .tar, .uu, .saveme, .dump and .bin files.