What Are External Referrers (Domains)?

Answer

External referrers are visits from domains that are not configured as part of your internal domains.

Definition

External Referrers (Domains) typically refer to external referrers coming from any domain that is not your own.

Depending on the settings of your Analytics site, it could be that you track two or more domains as your own internal domains. You might have this setup done if you own more than one domain and want to do cross-domain tracking.

Example: You own the domains "thisismydomain.com" and "thisismydomain.de" and "superdomain.com". You are linking between those domains and want to track visitor behavior between them, and you have told Siteimprove to set up all three sites as internal. The external traffic will be traffic from all domains that are not those three internal domains.