Multiple Website Domains - Reporting on Unique Users (De-Dupe)?

Hello, I have 4 websites (separate domains) for the “same” business - I am looking to be able to “roll-up” my reporting and report on the total UNIQUE number of users across all 4 website domains. What do you think the best way is to accomplish this?

Here’s the scenario:
We are a car dealership that has 3 buildings on the same property - Brand A, Brand B, and Brand C. Each brand requires us to have its own website.

Our websites are:

  1. DealerAllBrands .com
  2. DealerBrandA .com
  3. DealerBrandB .com
  4. DealerBrandC .com

The same customer will often visit 2 or more of our 4 websites, but we can only sell them 1 car, so we want to count them as 1 user for reporting purposes. We do not want to double-count users who visit multiple websites.

There are no links on any of the websites that a user can click on to get from to for example, so I don’t think cross-domain tracking via the pk_vid URL parameter would work? There are also no logins or anything that I can use to identify a user.

A customer ends up visiting multiple websites naturally - for example, they click on a Google Ad for and then later that day click on a Facebook Ad for

Is there any way that I can track the unique number of users (de-dupe) across all 4 websites?

I know by default a domain can’t access the cookies from another domain. But is it possible when a user visits Site A, to also set a cookie on Site B and Site C?

Or via browser fingerprinting?

Hi Ryan!

I think you should be able to achieve this with cross-domain tracking and session ID (or fingerprint in other words) enabled. The downside of this approach is that the consent form (in case it’s enabled) will pop up on each domain and ask the visitor for consent.