ERR_SSL_PINNED_KEY_NOT_IN_CERT_CHAIN
ERR_SSL_PINNED_KEY_NOT_IN_CERT_CHAIN Error
What This Error Means
The ERR_SSL_PINNED_KEY_NOT_IN_CERT_CHAIN error occurs when HTTP Public Key Pinning (HPKP) fails. The website has previously told the browser to only accept a specific public key (pin), but the certificate currently presented by the server does not match that pin. This protects against certificate misissuance but can lock users out if misconfigured.
Common Causes
- The website owner rotated their SSL certificate but forgot to update the pins.
- The backup pin was not deployed correctly.
- A Man-in-the-Middle (MITM) attacker is presenting a fake certificate.
- The browser has cached an old pin that is no longer valid.
How to Fix It (For Users)
- 1 Clear your browser cache and HSTS/HPKP settings (chrome://net-internals/#hsts).
- 2 Wait for the pin cache to expire (if set with a short max-age).
- 3 Contact the site owner.
For Site Owners / Developers
- Ensure your new certificate matches one of the pinned keys.
- Always have a backup pin for a separate key pair.
- Stop using HPKP (it is deprecated) and switch to Certificate Transparency (CT) monitoring.
- If locked out, you may need to wait for the `max-age` to expire for users.
When It Is NOT Your Fault
If the site owner mismanaged their key pinning strategy.
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