A referrer string is used to track which website a web user arrived from when navigating to a new website. It’s a small packet of data transmitted by a browser and recorded in the log files of the server. The same data can also be saved by tracking websites that the website owner is engaged with, such as Google Analytics.
Referrer strings are used so that web owners understand where their traffic is coming from. They can give web owners an insight into the proportion of traffic they’re generating from search engines, from social media, or by referrals from other sites that the website owner may be obliged to pay a commission.
