Adobe uses a cookie to track unique browsers/devices.
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)|
|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.