Attribution
Referring domain
Also called referrer host.
Referring domain is the host name part of the referrer, with the path removed. It tells you which site sent the visit.
How it is measured
The tool parses the referrer and keeps only the host, such as news.example.com or example.org. Subdomains may be grouped or separate depending on the setting.
Check the list for noise: your own domains, payment providers, and login services will appear as referrers and distort the report unless excluded.
Worked example
A software-docs site gets traffic from 214 referring domains in a month. The top one is its own marketing site at 2,250 sessions, then a developer forum at 1,420, then a payment provider at 380.
The owner removes the marketing site and payment provider as internal. The developer forum is now the biggest real external source. The owner contributes a guide there and sessions double to 2,900 the next month.
How it differs
A referring domain is a host. A referrer is the full address including the page. The host helps you count sites; the full address helps you find the page.
Common errors
Leaving internal domains in the list. Grouping subdomains incorrectly. Counting sessions from a spam domain as real. Ignoring domains that send many sessions with zero engagement. Looking only at the top ten.
In practice
Add your own domains and payment providers to the exclusion list. Review the top 20 referring domains monthly. Mark any that look like spam.