What is MIME type "application/x-msdownload"?

A MIME type is a string that tells browsers and other tools how to handle a particular kind of file.

application/x-msdownload is a MIME type used for executable files on Windows.
It signals that a file can be run directly by the operating system and usually contains compiled code or scripts.
Files with this MIME type can alter system settings or launch programs, so they must be handled with care.

Primary use case: Delivering executable content for installations and updates.
Key functionality: Identifies files that contain code meant for execution.
Security note: Running these files can affect your system. Only use sources you trust.

Files using this MIME type often have extensions such as DLL, BAT, and COM.
Each of these file types serves a different role. For example, the DLL is a dynamic link library used by multiple programs, the BAT is a batch script that automates tasks, and the COM is a command executable.
This MIME type remains central to ensuring that Windows knows how to safely handle and execute specific file types.

Associated file extensions

.dll, .bat, .com

Usage Examples

HTTP Header

When serving content with this MIME type, set the Content-Type header:


    Content-Type: application/x-msdownload

HTML

In HTML, you can specify the MIME type in various elements:


    <a href="file.dat" type="application/x-msdownload">Download file</a>

Server-side (Node.js)

Setting the Content-Type header in Node.js:


    const http = require('http');
    
    http.createServer((req, res) => {
      res.setHeader('Content-Type', 'application/x-msdownload');
      res.end('Content here');
    }).listen(3000);

Associated file extensions

.dll, .bat, .com

FAQ

What is a MIME type?

A MIME (Multipurpose Internet Mail Extensions) type is a standard that indicates the nature and format of a document, file, or assortment of bytes. MIME types are defined and standardized in IETF's RFC 6838.

MIME types are important because they help browsers and servers understand how to process a file. When a browser receives a file from a server, it uses the MIME type to determine how to display or handle the content, whether it's an image to display, a PDF to open in a viewer, or a video to play.

MIME types consist of a type and a subtype, separated by a slash (e.g., text/html, image/jpeg, application/pdf). Some MIME types also include optional parameters.

How do I find the MIME type for a file?

You can check the file extension or use a file identification tool such as file --mime-type on the command line. Many programming languages also provide libraries to detect MIME types.

Why are multiple MIME types listed for one extension?

Different applications and historical conventions may use alternative MIME identifiers for the same kind of file. Showing them all helps ensure compatibility across systems.