A referrer is an HTTP header field sent by a web browser when a browser requests to load a page. The referrer field identifies the request's source and provides information about the website or source linked to the destination page.
The referrer field is an important element of the HTTP protocol because it enables the tracking and analysis of referral traffic. However, the referrer field can also pose a privacy risk because it can potentially disclose users' browsing history and activity to the destination website. For this reason, some web browsers allow users to control the sending of the referrer field or to block it altogether.