Analytics provides several mechanisms by which visitors can be identified (listed in Analytics Visitor IDs). Regardless of the method used to identify a visitor, in data feeds the final visitor ID used by Analytics is split across the post_visid_high and post_visid_low columns, even when using the Experience Cloud ID Service.
To identify unique visitors:
If you would like to determine which mechanism was used to determine the visitor ID value (for example, to calculate cookie acceptance), the post_visid_type contains a lookup key that indicates which ID method was used. The lookup keys are listed along with the visitor ID mechanisms in the table below.
The Experience Cloud Visitor ID is reported in a separate column, mcvisid. Because this ID is reported in its own column, it can be unclear if Analytics is using this ID or a different ID to identify a visitor.
If the Experience Cloud Visitor ID was used to identify the visitor, the ID will be contained in the post_visid_high and post_visid_low columns and the post_visid_type will be set to 5. When calculating metrics, you should use the value from the post_visid_high and post_visid_low columns since these columns will always contain the final visitor ID.
Tip: When using the Adobe Analytics visitor ID as a key for other systems, always use post_visid_high and post_visid_low. These fields are the only visitor ID fields guaranteed to have a value with every row in the data feed.
There are several ways a visitor can be identified in Analytics (listed in the following table in order of preference):
|Order Used||Query Parameter (collection method)||post_visid_type column value||Present When|
|vid (s.visitorID)||0||s.visitorID is set.|
|aid (s_vi cookie)||3||Visitor had an existing s_vi cookie before you deployed the ID Service, or you have a Visitor ID grace period configured.|
|mid (AMCV_ cookie set by Experience Cloud ID Service)||5||Visitor's browser accepts cookies (first-party), and the Experience Cloud ID Service is deployed.|
|HTTP Mobile Subscriber header||2||Device is recognized as a mobile device.|
|IP Address, User Agent, Gateway IP Address||1||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 that list as the official visitor ID, and split that value across the post_visid_high and post_visid_low columns. 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.