What is MIME type "application/rsd+xml"?

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

application/rsd+xml is a MIME type for XML files that follow the Really Simple Discovery specification.

This format provides a simple way for websites to publish their service information. Instead of manually configuring endpoints, software such as blog editors and feed readers can automatically discover how to interact with a site.

It standardizes the discovery of services like blog APIs.
It helps client applications connect to website features without extra setup.
It often appears on blog and content management platforms to expose remote publishing capabilities.

Files using this MIME type carry the RSD extension. Their XML structure lists details such as API endpoints and preferred protocols.

For more technical background and real-world examples, see Really Simple Discovery.

Associated file extensions

.rsd

Usage Examples

HTTP Header

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


    Content-Type: application/rsd+xml

HTML

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


    <a href="file.dat" type="application/rsd+xml">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/rsd+xml');    
      res.end('Content here');    
    }).listen(3000);

Associated file extensions

.rsd

FAQs

What is the primary purpose of the application/rsd+xml MIME type?

This MIME type identifies files used for Really Simple Discovery (RSD), an XML format that describes how to interact with a web service. It is primarily used by blogging platforms to tell client software (like offline blog editors) where to find API endpoints for editing and publishing content.

How do I open or edit a file with the .rsd extension?

Since files served as application/rsd+xml are text-based XML documents, you can open them with any standard text editor like Notepad, TextEdit, or VS Code. Most web browsers will also display the XML structure directly if you navigate to the file URL.

Why do I see a link to application/rsd+xml in my WordPress site's header?

WordPress automatically generates an RSD link to enable XML-RPC or REST API discovery. This allows external tools, such as the WordPress mobile app or desktop blog editors, to automatically detect how to connect to your site without requiring you to manually input API URLs.

How do I configure Apache to serve .rsd files correctly?

To ensure your Apache server sends the correct application/rsd+xml header, add the following line to your .htaccess file or main configuration: AddType application/rsd+xml .rsd. Without this, servers might default to sending it as text/xml or text/plain.

Is application/rsd+xml the same as an RSS feed?

No, they serve different purposes. While both use XML, RSS (application/rss+xml) is designed for content syndication (reading posts), whereas RSD (application/rsd+xml) is designed for service discovery (finding where to write or edit posts). You can read more about file extensions generally at file-extension/rsd.

Are there security risks associated with exposing an RSD file?

The file itself is harmless, but it exposes the location of your site's API endpoints (like xmlrpc.php). If you do not use external publishing tools, some security experts recommend disabling the RSD link to slightly reduce the visibility of these attack vectors to bots.

What should I do if my browser downloads the .rsd file instead of displaying it?

This usually happens because the server is sending a Content-Disposition: attachment header or the browser doesn't have a built-in handler for application/rsd+xml. This is normal behavior for specialized XML formats; you can simply open the downloaded file in a text editor to view the contents.

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.