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Enhance Website Security with HSTS Preloading: A Step-by-Step Guide

HTTP Strict Transport Security (HSTS) is a crucial security mechanism that ensures websites enforce HTTPS connections to protect users from potential security threats. By preloading HSTS settings on Chrome and Firefox, you can enhance website security and build user trust. In this comprehensive guide, we will walk you through the essential steps to successfully preload your HSTS settings and provide useful recommendations to optimize security.

Understanding HSTS Preloading

HSTS Preloading is the process of submitting your website’s domain to major browsers’ preload lists. Once added, these browsers will automatically enforce HTTPS connections for your domain and all subdomains. This ensures users always access your website securely, reducing the risk of man-in-the-middle attacks and unauthorized eavesdropping. For more details on HSTS preloading, you can refer to the official documentation .

Submission Requirements

Before submitting your domain for HSTS preloading, ensure that your website meets the following essential requirements:

  1. Valid Certificate: Your website must serve a valid SSL or TLS certificate to enable secure HTTPS connections.

  2. HTTP to HTTPS Redirection: Ensure that all HTTP requests are redirected to their HTTPS counterparts when your website listens on port 80.

  3. HTTPS for all Subdomains: All subdomains of your website must support HTTPS connections to be eligible for HSTS preloading.

  4. HSTS Header on Base Domain: Include an HSTS header on your base domain for HTTPS requests with the following settings:

    • max-age must be at least 31536000 seconds (1 year).
    • The includeSubDomains directive must be specified to include all subdomains.
    • The preload directive must be specified to request inclusion in the preload list.

Here is an example of a valid HSTS header:

Strict-Transport-Security: max-age=63072000; includeSubDomains; preload

How to Preload HSTS Settings

If your website is fully committed to HTTPS and meets the above requirements, follow these crucial steps to successfully preload your HSTS settings:

  1. Examine Subdomains: Ensure that all subdomains of your website work correctly over HTTPS to provide a seamless browsing experience for users.

  2. Gradual Ramp-up: To test and fix any potential issues, add the HSTS header to your HTTPS responses with a low max-age value (e.g., 300 seconds). Gradually increase the max-age value in stages:

    • 5 minutes: max-age=300; includeSubDomains
    • 1 week: max-age=604800; includeSubDomains
    • 1 month: max-age=2592000; includeSubDomains
  3. Monitor Metrics: During each stage, closely monitor your website’s metrics, including traffic and revenue, to identify and address any issues before proceeding to the next stage.

  4. Increase max-age to 2 Years: Once you’re confident there are no more issues, set the max-age to 2 years (63072000 seconds) and add the preload directive to the HSTS header:

Strict-Transport-Security: max-age=63072000; includeSubDomains; preload
  1. Submit Your Site: After implementing the 2-year max-age setting, submit your site to the HSTS preload list using the form available on . Note that inclusion in the preload list may take several months to reach users with a Chrome update.

Opt-In for HSTS Preloading: Empowering Site Operators

Supporting HSTS preloading is an excellent security practice that enhances website protection. However, it should be an opt-in decision for site operators. If you provide HTTPS configuration advice or offer an option to enable HSTS, avoid including the preload directive by default. This approach prevents unintended inclusion in the preload list, which can lead to difficulties accessing certain subdomains.

To ensure a smooth experience, inform site operators about the long-term consequences of preloading and emphasize the importance of meeting all requirements before enabling HSTS for their domain.

Removal from the Preload List: A Deliberate Decision

Inclusion in the preload list is a permanent decision that cannot be easily undone. However, if you encounter strong technical or cost-related reasons preventing HTTPS support for certain subdomains, you have the option to request removal from Chrome’s preload list through the removal form .

Ensure that you have carefully evaluated the implications before making this significant decision.

Safer Browsing Starts with HSTS Preloading

In conclusion, preloading your HSTS settings on Chrome and Firefox is a proactive step towards a safer web browsing experience for your users. By enforcing HTTPS connections, you protect sensitive data and build trust among your visitors. Follow the guidelines mentioned above to preload your HSTS settings successfully and enjoy enhanced website security.


  1. Chromium - HTTP Strict Transport Security (HSTS)
  2. HSTS Preload Submission
  3. Mozilla Web Security Guidelines
  4. Google Web Fundamentals - Security