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

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

application/x-javascript signals that a file contains JavaScript code. It informs the browser to execute the script rather than display it as plain text. This MIME type is used by files like JS.

Its main role is to enable interactive and dynamic behavior on web pages. The script can update content, respond to user actions, and communicate with servers—all on the client side.

• Dynamic Behavior: Scripts update and change webpage content without requiring a full page reload.
• Client-Side Processing: JavaScript handles user input, validates forms, and manages events directly in the browser.
• Legacy and Compatibility: Though modern sites often use text/javascript, many servers and browsers still recognize this MIME type.

Additional details are available at the MDN Web Docs on JavaScript.

Associated file extensions

.js

Usage Examples

HTTP Header

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

    Content-Type: application/x-javascript
  

HTML

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

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

Associated file extensions

.js