We recently implemented Adobe Analytics for a client and am currently testing tag implementation for them. Strangely i see both vid and fid firing for them. As far as i know , if the visitor id cookie is rejected, the code sets a first party cookie(fallback visitor identification method) using the site’s current domain known as the FID. Not sure why both are firing! Any thoughts?
P.S - we have implemented visitor stitching for this client- cross device tracking.
Let me add really quickly that if you are using the visitorID service, you may not see fid on the tracking call. Meaning if analyticsVisitorID (aid) or marketingCloudVisitorID (mid) is set and present on the tracking call, you should not be seeing fid. Otherwise, you should see fid on every tracking call.
This is standard functionality to send it through with every tracking call. There is server-side logic that will determine which id is used for visitor identification purposes.
In other words, it sounds like everything is happening as it should. :)