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

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

The MIME type application/x-mimearchive marks files that store an entire HTML page and its associated resources in one package.
This format bundles the original HTML, images, style sheets, and scripts into a single file for easier sharing and offline viewing.
Files of this type are often saved with the extensions MHT or MHTML.

Preservation: Ensures all page elements are contained together.
Sharing: Simplifies distribution of complete web pages as one file.
Archiving: Provides a snapshot of the page for future reference.

It uses a multi-part message format to embed various components within a single file.
The "x-" prefix indicates it is a non-standard type, common in many applications even without formal registration.
For more on MIME types, see MDN Web Docs on MIME types.

Associated file extensions

.mht, .mhtml

Usage Examples

HTTP Header

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


    Content-Type: application/x-mimearchive

HTML

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


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

Associated file extensions

.mht, .mhtml

FAQs

How do I open files with the application/x-mimearchive MIME type?

Files with this MIME type, typically using the .mht or .mhtml extension, are best opened with Microsoft Edge or Internet Explorer. While Google Chrome and Mozilla Firefox can often display them, you may need to install specific extensions or modify browser flags to enable full support for this archive format.

How do I configure Apache to serve MHT files correctly?

To ensure your Apache server serves these files with the correct headers, add the following line to your .htaccess file or server configuration: AddType application/x-mimearchive .mht .mhtml. This prevents browsers from misinterpreting the archive as plain text or generic binary data.

Is application/x-mimearchive a standard MIME type?

No, the x- prefix indicates that it is a non-standard or experimental type, originally popularized by Microsoft. While the IETF standard for MHTML is multipart/related, application/x-mimearchive is still widely used by Windows applications and email clients to identify bundled web pages.

Why does my browser download the .mht file instead of displaying it?

This occurs if the web server sends a Content-Disposition: attachment header or if the browser does not natively support rendering application/x-mimearchive content. If you are a developer, check your server headers; if you are a user, try opening the file locally by dragging it into a compatible browser window.

What is the difference between standard HTML and application/x-mimearchive?

Standard HTML files link to external resources like images and CSS, requiring a separate folder for assets. In contrast, application/x-mimearchive uses MIME encapsulation to bundle the HTML code and all external resources into a single file, making it easier to email or store offline.

Are there security risks associated with MHT files?

Yes, because these archives contain HTML and potentially JavaScript, they can be used to execute malicious code or facilitate phishing attacks. Treat application/x-mimearchive files received from unknown sources with the same caution you would use for executable programs or standard HTML attachments.

How do I configure Nginx for application/x-mimearchive?

You should update your mime.types file or the types block in your Nginx configuration. Add the entry: application/x-mimearchive mht mhtml;. After saving the changes, reload Nginx to ensure the server delivers the correct content type header to clients.

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.