list of URLs to notify if a user follows the hyperlink
referrerpolicy
no-referrer
Specifies that no referrer information is to be sent along with requests to any origin.
no-referrer-when-downgrade
Sends a request’s full referrerURL stripped for use as a referrer for requests: whose referrerURL and current URL are both potentially trustworthy URLs, or whose referrerURL is a non-potentially trustworthy URL.
origin
Specifies that only the ASCII serialization of the request’s referrerURL is sent as referrer information when making both same-origin-referrer requests and cross-origin-referrer requests.
origin-when-cross-origin
Specifies that a request’s full referrerURL is sent as referrer information when making same-origin-referrer requests, and only the ASCII serialization of the origin of the request’s referrerURL is sent as referrer information when making cross-origin-referrer requests.
same-origin
Specifies that a request’s full referrerURL is sent as referrer information when making same-origin-referrer requests.
strict-origin
Sends the ASCII serialization of the origin of the referrerURL for requests: whose referrerURL and current URL are both potentially trustworthy URLs, or whose referrerURL is a non-potentially trustworthy URL.
strict-origin-when-cross-origin | empty
Specifies that a request’s full referrerURL is sent as referrer information when making same-origin-referrer requests, and only the ASCII serialization of the origin of the request’s referrerURL when making cross-origin-referrer requests: whose referrerURL and current URL are both potentially trustworthy URLs, or whose referrerURL is a non-potentially trustworthy URL.
unsafe-url
Specifies that a request’s full referrerURL is sent along for both same-origin-referrer requests and cross-origin-referrer requests.