What is MIME type "application/x-ns-proxy-autoconfig"?

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

application/x‑ns‑proxy‑autoconfig is the MIME type for a Proxy Auto‑Config file. This file contains JavaScript code that tells a browser how to set up its proxy connection automatically.
It often defines rules on when to use a proxy or make a direct connection, based on URL patterns or network conditions.

• It streamlines proxy configuration in dynamic network environments.
• It allows centralized control of proxy rules without manual client setup.
• It is commonly used in business and large network settings for efficient traffic routing.

The file is usually saved with the PAC extension. Browsers fetch and execute this file to determine the best way to connect to web resources. For more information, see Proxy Auto‑Config on Wikipedia.

Associated file extensions

.pac

Usage Examples

HTTP Header

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

    Content-Type: application/x-ns-proxy-autoconfig
  

HTML

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

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

Associated file extensions

.pac