Guide to Setting the "Cross-Origin-Embedder-Policy" Header

Contents

What Does This Header Do?

The Cross-Origin-Embedder-Policy (COEP) header enhances security by ensuring that resources your website embeds (like scripts or images) are only loaded from trusted origins that explicitly grant permission. This is crucial for enabling powerful features like SharedArrayBuffer while maintaining a secure browsing environment.

Steps to Set the Header

1. If You Use a Web Server (e.g., Apache, Nginx, etc.)

For Apache:

  1. Open your website's configuration file (or .htaccess file if you use one).
  2. Add the following line: 
    Header set Cross-Origin-Embedder-Policy "require-corp"
  3. Save the file and restart the Apache server to apply changes.

For Nginx:

  1. Open your website's configuration file (e.g., /etc/nginx/sites-available/your-site).
  2. Add the following line inside the server block: 
    add_header Cross-Origin-Embedder-Policy "require-corp";
  3. Save the file and restart Nginx to apply changes using: 
    sudo systemctl restart nginx

2. If You Use a Programming Language:

For PHP:

header("Cross-Origin-Embedder-Policy: require-corp");

For Node.js:

Use a middleware like helmet to set the header automatically:

const helmet = require('helmet');
app.use(helmet.crossOriginEmbedderPolicy({ policy: 'require-corp' }));

Or set it manually:

app.use((req, res, next) => {
  res.setHeader('Cross-Origin-Embedder-Policy', 'require-corp');
  next();
});

For Python (Flask):

from flask import Flask, Response

app = Flask(__name__)

@app.after_request
def set_headers(response):
    response.headers['Cross-Origin-Embedder-Policy'] = 'require-corp'
    return response

3. Verify the Header

After setting the header, test your website to ensure it’s working:

  1. Open your website in a browser.
  2. Use the developer tools (right-click > Inspect > Network tab) to view the HTTP headers.
  3. Look for the Cross-Origin-Embedder-Policy header with the correct value.

Why It Matters

Setting this header protects your website from cross-origin attacks by ensuring only trusted resources are embedded. It also enables advanced browser features like SharedArrayBuffer, enhancing performance while maintaining security.