What's the difference between "Portal sites" and "Referrer sites"?

Portal sites and Referrer sites are two traffic source categories used to distinguish internal referral traffic (within your organization) from external referral traffic (outside your organization).

Referrer sites

The Referrer sites traffic source includes all visits that originated from a site outside of your organization.

This classification is based on the referrer information provided by the visitor’s browser, which indicates the webpage (and domain) where the user was immediately before arriving on your site.

Portal sites

The Portal sites traffic source includes all visits originating from URLs that are recognized as belonging to other sites in your organization.

These “portal” domains are typically sites that are registered within your organization’s scope/contract and are known to the platform as part of your web property network. This allows Piano Analytics to separate cross-site navigation within your organization from true external referrals.

Example

Assume:

• Site A: the site you are analyzing

• Site B: another site owned by your organization (recognized within your organization’s scope)

• Site C: an external site not owned by your organization

Then:

• Visits from Site B → Site A are categorized as Portal sites

• Visits from Site C → Site A are categorized as Referrer sites

Why this distinction matters

Separating Portal sites from Referrer sites helps you analyze:

• how users move between your organization’s sites (internal network traffic), and

• how much traffic is being driven by third-party sites (external referrals)

This makes it easier to interpret referral performance without mixing internal cross-domain navigation with external acquisition sources.