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An external referrer is any site that links to your Confluence instance. Each time someone clicks on the external link, your Confluence site can record the click as a referral.
You can exclude external referrers to prevent them from being recorded or displayed anywhere on your site. Once you have specified your list of blocked URLs, any incoming links from URLs that match the list will no longer be recorded. Referrer URLs are blocked if they start with any of the URLs in the exclusion list. So http://evilspamsite.blogspot.com will also match http://evilspamsite.blogspot.com/nastypage.html
There are two instances where you may want to do this:
You need to be a Confluence administrator and to know the URL of the site to add it to the excluded referrers list.
To add a URL to the excluded referrers list:
You can add multiple URLs to the list.