An octet stream is the binary version of a MIME-type file. MIME-type files are those sent and received through browsers, servers and web clients. An octet is an eight-bit byte. An octet-stream file may be any file format such as an .exe or .jpeg renamed during transmission from source to destination. Octet streams are also known as byte streams.
Browsers and email clients routinely rename files with missing extensions to octet streams. If having trouble opening an octet-stream file, one should attempt to rename the file extension if the file type is known or displayed when downloading an attachment. If the file type is unknown and cannot be easily determined, ask the sender about the file type before attempting to rename the file. If an extension is properly renamed, the file should now open easily. Another option is to open the appropriate program for the file type and attempt to open the file in the program without renaming the extension. Be sure to open the file in the appropriate application based on the file type. Octet-stream files are usually executable application files. If still having trouble opening a file, request that the sender attempt to retransmit the file. Email or web clients are rarely able to open octet stream files, but may be able to determine the appropriate program to open the file.