Can ECID enable cross-site retargeting based on previous browsing behaviour?

[ab_cdef]

This might sound like a dumb question, but I’m asking anyway because it’s definitely out of my depth:

If a visitor lands on a website for the first time, they’re assigned an ECID. Let’s say they browse a few product pages and then leave without doing anything else (like creating an account or adding to cart). If they use the same browser to visit YouTube the next day, will the ECID still be retained? And can we start showing them ads based on the product pages they looked at on the website?

Thanks

[Harveer_SinghGi1]

Hi @ab_cdef,

ECID will be retained if the ID Service on both of these sites is using the same Org ID as the ECID returned by ID Service is based on the Demdex Cookie value and the Org ID sent with the ID request. If this is true, you should be able to personalize the YouTube content for users based upon their browsing history on the previous website.

However, if the ID Service is using different Org IDs on the website and YouTube then ECID will change and the user is treated as two separate users on these sites.

Here is the documentation that talks about how ECID is set:

https://experienceleague.adobe.com/en/docs/id-service/using/intro/id-request

[Rite18]

@ab_cdef it is possible provided those sites are part of the same Experience Cloud organization, and approach to have Unified ECID or AEP over AAM where you can FPID [server-based ECID ] implementation, as ECID is not unique across requests which would have duplicate in terms of AAM based implementation 

[bjoern__koth]

Since YouTube is not your domain, and as the others have mentioned, the orgID is surely different, the ECID cannot be restored on Google side.

The Demdex cookie is a third party cookie that can be leveraged across domains, but in times of cookie lifetime limitations for third party cookies, this is slowly becoming less and less useful.

There are ways to transport the ECID between domains, if you have a link on domainA, pointing to domainB yet again, this only works on direct links between A and B and not of the user manually opens domainB after he has visited domainA