Referral traffic in Google Analytics refers to the segment of traffic that arrives on a website through another source, such as a link on another domain. Referral traffic is one of three statistics tracked by Google Analytics. It is important to track referral traffic because it sends potentially valuable visitors to a website from trusted domains while getting the content in front of new people. Referral traffic can come from backlinks, which are frequently passed from one social group to another.

To view referral traffic sources in Google Analytics, one can log into their Analytics account and click on "Traffic Sources" followed by "Referrals" on the left-hand side. A graph will display showing traffic for a one-month period, and below it, a table displays the names of domains referring traffic to the site, as well as statistics on how visitors react to what they see on the site.

It is possible to exclude traffic referred from selected domains by creating a filter in Google Analytics. This can be useful to prevent spam hits from polluting legitimate hit data. A referral exclusion filter works by comparing the filter pattern provided with the hit values found in the Campaign Source dimension.

Referral traffic is not only a potentially large source of overall traffic for a site, but it also means that other sites are linking to it, which boosts its SEO and helps it rank higher in search engines. By analyzing which sites are sending referral traffic, one can make changes and marketing decisions that will grow their business.