Identifying Unique Visitors

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Analytics Visitor ID Order

Adobe Analytics provides several mechanisms to identify visitors. The following table lists the different ways a visitor can be identified in Analytics (in order of preference):

Order Used Query Parameter (collection method) Present When
vid (s.visitorID) s.visitorID is set
aid (s_vi cookie) Visitor had an existing s_vi cookie before you deployed the Visitor ID service, or you have a visitor ID grace period configured.
mid (AMCV_ cookie set by Marketing Cloud Visitor ID service) Visitor's browser accepts cookies (first-party)
fid (fallback cookie on H.25.3 or newer, or AppMeasurement for JavaScript) Visitor's browser accepts cookies (first-party)
IP Address, User Agent, Gateway IP Address Visitor's browser does not accept cookies.

In many scenarios you might see 2 or 3 different IDs on a call, but Analytics will use the first ID present from the previous table as the official visitor ID. For example, if you are setting a custom visitor ID (included in the "vid" query parameter), that ID will be used before other IDs that might be present on that same hit.

Note: Each Analytics visitor ID is associated with a visitor profile on Adobe servers. Visitor profiles are deleted after at least 13 months of inactivity regardless of any visitor ID cookie expiration.