Guide to Setting the "Strict-Transport-Security" Header

Contents

What Does This Header Do?

The Strict-Transport-Security (HSTS) header tells browsers to only communicate with your website over HTTPS, preventing insecure HTTP connections and mitigating certain attacks like man-in-the-middle (MITM).

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 Strict-Transport-Security "max-age=31536000; includeSubDomains"
  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 Strict-Transport-Security "max-age=31536000; includeSubDomains";
  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("Strict-Transport-Security: max-age=31536000; includeSubDomains");

For Node.js:

Use a middleware like helmet to set the header automatically:

const helmet = require('helmet');
app.use(helmet.hsts({ maxAge: 31536000, includeSubDomains: true }));

Or set it manually:

app.use((req, res, next) => {
  res.setHeader('Strict-Transport-Security', 'max-age=31536000; includeSubDomains');
  next();
});

For Python (Flask):

from flask import Flask, Response

app = Flask(__name__)

@app.after_request
def set_headers(response):
    response.headers['Strict-Transport-Security'] = 'max-age=31536000; includeSubDomains'
    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 Strict-Transport-Security header with the correct value.

Why It Matters

Setting this header ensures that your website is only accessible via secure HTTPS connections, protecting user data and preventing potential attacks like man-in-the-middle (MITM) or downgrade attacks.