In web analytics, the referrer (or referer) is the URL of the last external page a user visited before landing on the analyzed page. It is a way to record user origin from the moment the user arrives on the site, which in turn can indicate patterns in traffic sources (SEO, partner sites, direct traffic – if no referrer).
This information is provided by the browser thanks to the HTTP protocol, in a variable called “document.referrer.
If the origin of the visit cannot be known via other means (URL settings), the referrer is a way to classify visits using referrals, and indicate the corresponding domain in classic web analytics tools.
