What is MIME type "application/x-font-otf"?

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

application/x-font-otf is a MIME type for OpenType Font files. It tells browsers and systems how to handle these font files.

Main use: It supports scalable font rendering for high-quality text display.
Web design: It enables custom typography on websites by delivering consistent font styling across browsers.
Desktop publishing: It helps design software display detailed, scalable fonts for print and digital media.
Technical aspect: The "x-" prefix indicates it is a non-standard type, though widely accepted and used.

Files using this MIME type are typically saved with the file extension OTF.

For more on OpenType fonts, you may check the OpenType Wikipedia page.

Associated file extensions

.otf

Usage Examples

HTTP Header

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


    Content-Type: application/x-font-otf

HTML

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


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

Associated file extensions

.otf

FAQs

Is application/x-font-otf the standard MIME type for OpenType fonts?

No, the official IANA standard is now font/otf. The application/x-font-otf type is a legacy or non-standard version often found in older server configurations, though most modern browsers will still process it correctly.

How do I add application/x-font-otf to an Apache server?

You can define the type in your .htaccess file or main configuration to ensure correct delivery. Add the line AddType application/x-font-otf .otf to map the MIME type to the .otf file extension.

How do I declare an OTF font in CSS using @font-face?

You should specify the source URL and the format string in your CSS. For example: src: url('myfont.otf') format('opentype');. While the server sends the MIME type, the CSS format hint helps the browser select the correct resource.

Why is my OTF font blocked by CORS errors?

Fonts served from a different domain (like a CDN) often trigger Cross-Origin Resource Sharing (CORS) security policies. To fix this, ensure your web server sends the header Access-Control-Allow-Origin: * (or your specific domain) when serving application/x-font-otf files.

How do I configure Nginx to serve OTF files?

Edit your mime.types file, typically found in /etc/nginx/. Add or verify the line application/x-font-otf otf; inside the types { } block, then reload Nginx to apply the changes.

What does the "x-" prefix mean in application/x-font-otf?

The x- prefix indicates that the MIME type was originally defined as a non-standard or experimental subtype. While widely supported, it has largely been superseded by the standardized font/otf type in modern web development.

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.