Identifying Unique Visitors

The method for identifying unique visitors among multiple contexts includes a prioritized sequence to ensure accuracy in this determination. The following table shows this prioritized sequence:

Order used
Query parameter (collection method)
post_visid_type column value
Present when
1
vid s.visitorID
0
s.visitorID is set.
2
aid  s_vi cookie
3
Visitor had an existing s_vi cookie before you deployed the Visitor ID service, or you have a Visitor ID grace period configured.
3
mid AMCV_ cookie set by Identity Service
5
Visitor’s browser accepts cookies (first-party), and the Identity Service is deployed.
4
fid fallback cookie on H.25.3 or newer, or AppMeasurement for JavaScript
4
Visitor’s browser accepts cookies (first-party).
5
HTTP Mobile Subscriber header
2
Device is recognized as a mobile device.
6
IP Address, User Agent, Gateway IP Address
1
Visitor’s browser does not accept cookies.

For information on how unique visitors are reported, see Unique Visitors in Analytics.

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