Content Type Binary Octet Stream

What is Binary Octet Stream? The Octet-Stream is used for file attachments on the Web with an unknown file type. Those Octet-Stream files are arbitrary binary data files which may be in any multimedia format. The Octet-Stream format was developed for Web browsers to understand that the file attachment is in an unknown file type, that also lets you choose to download and save the attached file in any file format that you want.

In other instances, the Octet Stream file format is used to inform you as a user that the attached file can be saved in a recommended file format. This also lets the Web browser enable you for knowing the recommended file format for the attached Octet-Stream file. You have to know that those Octet-Stream files may be opened by renaming the extension of the attached file to a specific file extension, and then by using an application with support for opening such files. For instance, an Octet-Stream file can be renamed to a .txt file (if it is a .txt file), and then Notepad can be used to open the file. This means that you are required to know the file type of the attached Octet-Stream file before you rename the file in the correct file extension.

Content Type Binary Octet Stream


We are going to inform you again that an Octet Stream is the binary version of MIME-type file. The MIME-type files are those sent and received through the Browsers, Servers, and Web Clients. An octet is an 8-bit byte. For your information, an octet-stream file is able to be any file format such as a .jpeg renamed during transmission from source to destination. We get information that the Octet streams are known as byte streams. Usually, Browsers and Email Clients rename files with missing extensions to Octet Streams routinely.

If you have a problem when you are opening an octet-stream file, remember that one should rename the file extension if the file type is known once you are downloading an attachment. While if the file type is unknown and cannot be assigned easily, you are able to ask the sender regarding the file type before you rename the file. If an extension is renamed properly, now the file will open easily. Another method is to open the appropriate program for the file type and try to open the file in the program without renaming the extension. Make sure to open the file in the appropriate application based on the file type. Normally, the Octet-Stream files are executable application files. If you still have a trouble when you are opening a file, do not hesitate to request that the sender retransmit the file. In fact, Web Clients and Email are seldom opening the Octet Stream files, but they may be able to assign the appropriate program to open the file.


Apparently, there are two primary MIME types which are important for the role of default types, If you want to know those two primary MIME types, please look at the text below:

  • text/plain

This is the default value for the textual files. A textual file can be human-readable and must not contain binary data.

  • application/octet-stream

This is the default value for all other cases. An unknown file type is able to use this type. Browsers pay a particular care once manipulating those files, trying to safeguard the user to prevent harm behaviors.

For your information, IANA is the official registry of MIME types and maintains a list of all the official MIME types.


Now, you may want to know how to open an Octet-Stream. To open unidentified file, you need to figure out which program can open the file as a document or change the extension file to run as a program.

Files With Extensions

  • Please double-click the octet-stream file after downloading it. If the file contains a usable extension, it will load properly even if your email client or Web browser cannot identify it. Alternatively, Windows will show a list of programs to try using.
  • After that, you are able to click a program in the list to load the file by using the selected software. If you cannot see any options in the list, you have to click “More Options.” To select a specific program not found on the list, you are able to click at Look for Another App on This PC.
  • The next step is to check whether the file loads correctly or not. If it does not, you need to quit the program and try again with another application.
  • The last step, you have to double-click the file again, once you discover a working application. Afterwards, you need to navigate the box to click at ‘Use this app’ for all similar files and then take the correct program. For note: This will associate the extension with the choice application for the future use.

Files Without Extensions

  • Please double-click the file to display a list of programs on your PC. Pick one to try loading the file. If the file does not load correctly, you have to quit the program and try another.
  • After that, you have to select the file after knowing its type. In this step, you have to press “F2” to rename the file and type its extension after the file name. In an example, if you find a file to be a Word 2013 document, so you have to add “.docx” without quotes, and then press Enter. Next, the typed extension is going to disappear but the icon of the file is going to change, recognizing its new type.
  • The last step, you have to append the extension “.exe” if you run a file as an application, rather than as a document in another program. Files show as octet-stream files are often applications, however you only need to run a downloaded application if you trust its source.