Impact of Chrome Third party cookie deprecation on Adobe analytics Unique Visitors metric

Google has disabled the third party cookies for 1% of the chrome users in the first quarter of 2024 and google is planning to ramp up to 100% of Chrome users from early 2025. (more info)

As we all know, more than 50% of users worldwide uses Chrome browser. So, we should assess all the impact may occur due to third party cookie deprecation on chrome browser.

Latest update from Google
Instead of deprecating third-party cookies, google will introduce a new experience in Chrome to select cookies as per the use choice- more info.

Understanding Third Party Cookie

A third-party cookie is a cookie that’s placed on a user’s device — computer, cellphone or tablet — by a website from a domain other than the one the user is visiting. Third-party cookies are most frequently used to track user behavior across websites for online advertising. However, this practice has raised significant privacy concerns and in response, google chrome is phasing out third party cookie support. Please note, as of today Firefox and Safari browsers, by default does not supports third party cookies.

Does Adobe analytics uses Third Party Cookie?

If your analytics implementation solution uses Adobe Experience Cloud Identity Service to identify visitor, then this identity service uses third party cookie to identify visitor across websites. In this blog, I won’t discuss how this identity service works and store the cookies rather discuss what will happen to Adobe Unique Visitor metric when third party gets disabled.

For high level understanding, Adobe identity service dpm.demdex.net/id stores demdex third party cookie on the domain dpm.demdex.net, also stores AMCV cookie on first party domain to identify user for later visits to the website (more info). And when you have multiple websites under one Adobe Organization ID (more info), with this third party demdex cookie Adobe is able to identify same visitor.

If you are curious to know how Adobe Experience Cloud Identity Service works and how it stores cookies then this is THE Document- https://experienceleague.adobe.com/en/docs/id-service/using/intro/id-request

Impact on Adobe Unique Visitor metric when you have one website under one Adobe OrgID

There wont be any change or impact on Unique Visitor Metric due to third party cookie deprecation, because there is only one website.

As mentioned before, third party cookies mainly used across websites to share information. And Adobe Identity Service uses third party cookie (demdex) to identify same visitor across websites, as there is only one website under one OrgID then there wont be any impact.

Please understand, Chrome is just disabling ‘storing of third party cookies’ and not blocking of third party domain requests, meaning Adobe will be able to use dpm.demdex.net/id service request its just cookies wont be stored from dpm.demdex.net domain.

Impact on Adobe Unique Visitor metric when you have multiple websites under one Adobe OrgID

Before jumping to the impact, understand that when visitor visits the website first time, Adobe stores AMCV cookie on first party domain (more info) with default expiry as 2 years (more info). Meaning if user visits the same website within 2 years of time span then Adobe solution will use AMCV cookie for user identification and won’t call Identity service (dpm.demdex.net).

For simplicity lets assume there are two websites Web-A and Web-B. On both websites Adobe analytics is implemented and uses same Adobe OrgID.

• Existing Visitors : These are the visitors who have visited both websites Web-A and Web-B before third party cookie deprecation (Lets assume, during March-2024). Also remember, during user’s visit AMCV cookie is stored on the user’s device with 2 years of expiry as a first party cookie.
  After the third party cookie deprecation(lets assume third party cookies disabled on March-2025) , if user visits the Web-A and Web-B websites (during May-2025) then on both websites visitor will be treated as same visitor because of AMCV cookie, because this cookie is already available on the user’s device and has not expired yet. Meaning in the Adobe report if you run the Unique Visitor Metric against both website then you will see only 1 Unique Visitor.

• New Visitors: These are the visitors who will visit the Web-A and Web-B websites after third party cookie deprecation(lets assume third party cookies disabled on March-2025). Lets say user visits the Web-A and Web-B in the May-2025 month, then user will be treated as two separate visitor, because now Web-A and Web-B won’t be able to access the third party demdex cookie. In the Adobe report if you run the Unique Visitor Metric against both website then you will see 2 Unique Visitors.
  Also when you run report for only single website, then you won’t see any impact in Unique Visitors number, but when running the report for all websites under one Adobe OrgID then you may observe increase in Unique Visitors number.

Conclusion

After Third party cookie deprecation on chrome browser, if you have adobe analytics solution implemented on single website under one Adobe OrgID, then there wont be any impact on Unique Visitors metric.
If you have adobe analytics solution implemented on multiple websites under one Adobe OrgID, then when running Adobe Unique Visitors report for all websites together then you may observer slight increase in the Unique Visitors numbers, because now Adobe wont be able to identify the same visitor across websites.