Difference between application/x-javascript and text/javascript content types?

When serving JavaScript files, choosing the correct MIME type is crucial for proper browser handling. Let's explore the differences between these content types and understand which one to use.

text/javascript (Obsolete)

The text/javascript content type was used in the early days of HTML but is now obsolete according to RFC 4329. While browsers still support it for backward compatibility, it should not be used in modern applications.

// Server header (obsolete)
Content-Type: text/javascript

application/x-javascript (Experimental)

application/x-javascript was an experimental content type, indicated by the "x-" prefix. The "x-" denotes non-standard or experimental MIME types that were not officially registered.

// Server header (experimental, avoid)
Content-Type: application/x-javascript

application/javascript (Recommended)

The correct and standardized content type for JavaScript is application/javascript. This is the official MIME type defined in RFC 4329 and should be used for all JavaScript files.

// Example: Setting correct content type in Node.js
const http = require('http');
const fs = require('fs');

const server = http.createServer((req, res) => {
    if (req.url === '/script.js') {
        res.setHeader('Content-Type', 'application/javascript');
        const jsContent = fs.readFileSync('script.js', 'utf8');
        res.end(jsContent);
    }
});

console.log('Server configured with correct MIME type');

Server configured with correct MIME type

Comparison

Browser Compatibility

All modern browsers correctly handle application/javascript. Using the wrong content type may cause issues with strict security policies or content filtering systems.

Conclusion

Always use application/javascript as the content type for JavaScript files. This ensures proper browser handling and compliance with modern web standards.