What is MIME type "text/x-opml+xml"?

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

text/x-opml+xml specifies files written in the Outline Processor Markup Language (OPML).
It denotes documents with an XML-based outline structure used to represent hierarchical data.

Main use: Exchanging and managing outline structures between software applications.
Additional uses: Organizing RSS feed lists, planning content, and sharing structured data among different programs.

It applies to the OPML file type. This MIME type signals that the file must be parsed as XML to render and process the embedded outline correctly.
For more details on OPML, consider checking external sources such as Wikipedia.

Associated file extensions

.opml

Usage Examples

HTTP Header

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


    Content-Type: text/x-opml+xml

HTML

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


    <a href="file.dat" type="text/x-opml+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', 'text/x-opml+xml');    
      res.end('Content here');    
    }).listen(3000);

Associated file extensions

.opml

FAQs

What is the primary purpose of the text/x-opml+xml MIME type?

This MIME type identifies documents written in Outline Processor Markup Language (OPML). It is most commonly used to import and export lists of subscription feeds (RSS/Atom) between news aggregators, podcast players, and outline processors.

How do I configure an Apache server to serve OPML files correctly?

You can ensure the correct Content-Type header is sent by adding a directive to your .htaccess file or server config. Use the line: AddType text/x-opml+xml .opml.

Why do some servers serve OPML files as text/xml instead?

Since OPML is strictly valid XML, generic web server configurations often default to text/xml or application/xml for .opml files. However, using text/x-opml+xml provides a more specific indicator to the client software regarding the file's schema and intended usage.

How do web browsers handle text/x-opml+xml files?

Most modern browsers (like Chrome or Firefox) do not have a built-in OPML viewer. They typically treat the file as generic XML and display the raw DOM tree (code view) or prompt the user to download the file. To view it as an outline, you need an extension or a dedicated RSS reader.

Is text/x-opml+xml a standard IANA MIME type?

No, the x- prefix indicates that it is a non-standard or experimental subtype. Despite this, it is the de facto standard used by the developer community and applications like Feedly, Thunderbird, and various podcast apps to identify OPML files.

Are there security risks associated with OPML files?

As an XML-based format, OPML files can theoretically be vectors for XML External Entity (XXE) attacks if processed by a poorly configured parser. However, for end-users simply importing a list of feeds into a reader, the risk is generally considered low compared to executable formats.

Can I open text/x-opml+xml files in a text editor?

Yes. Because OPML is plain text based on XML, you can open and edit these files in any standard text editor like Notepad, TextEdit, or VS Code. You will see a hierarchical structure of <outline> tags containing URLs and titles.

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.