HTTP Public Key Pinning (HPKP) allows websites to send an HTTP header that pins one or more of the public keys present in the site’s certificate chain. This feature tracks the implementation of HPKP reporting, which allows website owners to receive reports when the browser detects HPKP violations.
Docs: https://developers.google.com/web/updates/2015/09/HPKP-reporting-with-chrome-46 https://docs.google.com/document/d/1hPMeG44li9hccIj4Jm2S3v1O_DEYnPsoiD4ZCzkAN8c/edit?usp=sharing https://developer.mozilla.org/en-US/docs/Web/Security/Public_Key_Pinning