What is MIME type "application/vnd.ms-cab-compressed"?

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

application/vnd.ms-cab-compressed is a MIME type that defines a compressed archive format from Microsoft.
It bundles several files into one package for compact storage and easy distribution.
This format makes it simpler for Windows to install software, drivers, and system updates. It also supports digital signatures for security.
The type is often seen in the following scenarios:
Files associated with this MIME type include formats such as CAB for general archives, IMS for skins, XSN for form templates, IMA for animations, MSU for update packages, and others like IMF, IMN, IME, IMW, DEVICEMETADATA-MS, DIAGCAB, and LTW.
Each linked file type serves specific roles within its application environment, reinforcing how versatile the CAB format can be.

Associated file extensions

.cab, .ims, .xsn, .ima, .msu, .imf, .imn, .ime, .imw, .devicemetadata-ms, .diagcab, .ltw

Usage Examples

HTTP Header

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


    Content-Type: application/vnd.ms-cab-compressed

HTML

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


    <a href="file.dat" type="application/vnd.ms-cab-compressed">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/vnd.ms-cab-compressed');    
      res.end('Content here');    
    }).listen(3000);

Associated file extensions

.cab, .ims, .xsn, .ima, .msu, .imf, .imn, .ime, .imw, .devicemetadata-ms, .diagcab, .ltw

FAQs

How do I configure a web server to serve CAB files with the correct MIME type?

To ensure browsers and operating systems handle these files correctly, you should explicitly define the MIME type. For Apache, add AddType application/vnd.ms-cab-compressed .cab .msu to your .htaccess or config file. For Nginx, add application/vnd.ms-cab-compressed cab msu; inside the types { } block in your mime.types or server configuration.

How do I open a file sent as application/vnd.ms-cab-compressed?

Since this format is a Windows native archive, you can usually double-click files like .cab or .msu in Windows to open or install them. To view or extract the contents of a generic CAB file without installing it, you can use third-party archivers like 7-Zip, WinRAR, or the Windows command-line tool expand.

Why does my browser download the file instead of running the installation automatically?

Browsers treat application/vnd.ms-cab-compressed as a binary download for security reasons. Executing system updates or driver installations directly from the web without user intervention would be a security risk. You must save the file to your disk and manually execute it to apply the update or install the component.

Are files with this MIME type safe?

Files using this type, such as MSU updates or DIAGCAB diagnostics, often modify system files. While the format supports digital signatures to verify the author (usually Microsoft), you should only run these files if you downloaded them from a trusted source.

What is the relationship between this MIME type and InfoPath XSN files?

Microsoft InfoPath form templates (XSN) are actually renamed Cabinet archives containing XML data and schema definitions. Because they use the CAB compression structure internally, they are often identified by the application/vnd.ms-cab-compressed MIME type during transmission or file analysis.

Can I use application/octet-stream instead of the specific CAB MIME type?

Yes, application/octet-stream is a generic fallback that forces a file download, which works for most binary archives. However, using the specific application/vnd.ms-cab-compressed type is better practice as it allows browser plugins, antivirus software, and the OS to immediately recognize the file as a Microsoft Cabinet archive.

General 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.