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MIME Type
application/octet-stream
BinaryGeneric MIME type for arbitrary binary data when a more specific type is not known.
MIME type reference, HTTP example, browser usage, common mistakes, and related content.
What is the application/octet-stream MIME type?
The MIME type application/octet-stream is used to tell browsers, APIs, and servers how a file or response body should be interpreted.
MIME stands for Multipurpose Internet Mail Extensions, and MIME types are now a standard part of HTTP responses and web content delivery.
When a browser or client receives a response with application/octet-stream, it uses that information to decide how the content should be processed, rendered, downloaded, or executed.
Example
Content-Type: application/octet-stream
HTTP example
HTTP/1.1 200 OK Content-Type: application/octet-stream Content-Length: 1256
Common file extensions
.bin
Common use cases
- Generic file downloads
- Unknown binary files
- Fallback file serving
Common mistakes
- Using the wrong MIME type for the file being served
- Returning text/plain instead of application/octet-stream
- Forgetting required parameters like charset when relevant
- Using a deprecated MIME type in older server configurations
- Serving assets with a mismatched Content-Type header, causing browser parsing issues
How browsers use it
Browsers use the Content-Type response header to decide how a response should be handled. For example, HTML is rendered as a page, CSS is parsed as styles, JavaScript is executed as script, and images are displayed visually. If the MIME type is incorrect, the browser may refuse to load the file correctly or may treat it as plain text or a download instead.
Developer note
Often used as a fallback for downloads, but a more specific MIME type is usually better.