Overview 

An HSTS error occurs when your browser is forced to use a secure (HTTPS) connection, but your website does not have a valid SSL certificate.

HSTS (HTTP Strict Transport Security) is a security policy that instructs browsers to only connect to a domain over HTTPS.

Why This Error Happens

You may see an HSTS error if:

• Your domain previously had SSL enabled and HSTS was set
• Your browser has cached an HSTS policy for the domain
• The website no longer has a valid SSL certificate

Because of this policy, the browser will:

• Force HTTPS connections
• Block access if the HTTPS connection is not valid

Important Behavior

• HSTS is cached per browser and per device
• Even if HSTS is removed from the server, browsers may continue enforcing it
• The cache duration depends on the HSTS “max-age” value and can persist for weeks or months

Can This Be Bypassed?

• HSTS can sometimes be cleared manually in a specific browser
• However, this only affects that device and browser instance
• It does not resolve the issue for other users globally

For this reason, bypassing HSTS is not recommended as a solution.

Common Causes

• SSL certificate is missing, expired, or not installed
• Domain is not pointing to the correct server
• DNS was recently updated and SSL has not yet been issued
• HSTS was previously enabled on the domain

How to Fix It

To properly resolve the issue:

1. Install a valid SSL certificate for the domain
2. Ensure the domain is pointing to the correct hosting server
3. Allow time for DNS propagation if changes were recently made

Once HTTPS is working correctly, browsers will be able to connect without errors.

Key Takeaway

An HSTS error means the browser requires a secure HTTPS connection, but the website does not currently have a valid SSL certificate. While it may be possible to bypass this locally, the correct fix is to restore a valid HTTPS configuration so the site works for all users.