No Cross-site Tracking

No cross-site tracking means a visitor identifier is scoped to one site's own domain and is never joined with that person's activity on other sites.

The identifier is kept as a first-party cookie or in browser storage under the site's own domain, so the same person picks up a different identifier on another site and no shared identity graph stitches the two together. The cost is explicit: retargeting audiences and following one person's journey across several domains are lost, unless cross-domain linking is configured deliberately and on its own legal basis. Browsers have been closing the same path for years by restricting third-party cookies, so cross-site tracking produces unstable data even where it is permitted. The common misreading is that no cross-site tracking means no identifier at all; the identifier exists, its scope is simply limited.