Cross-Domain Tracking, Where Needed

We begin by deciding whether you need it at all. We list every address a visitor might use: your main site, subdomains, an online shop on another domain, a hosted booking tool, a payment gateway, a separate microsite, a regional domain and a landing page platform. Subdomains of one registered domain share cookies, so they normally work without changes. Different domains do not, and each needs attention if both are part of one customer journey. We then trace actual journeys: from an ad or search result to the first page, through key steps and to a conversion. We use test visits, analytics reports on self-referrals and the browser’s network view to see where sessions break. Typical signs are your own domain or a payment provider appearing as a top referral, a jump in “direct” conversions, and conversions that show a landing page of the checkout domain. Next we decide which domains belong in one measurement. We add them to the data stream’s cross-domain settings so that the tracking script adds a small linker parameter to links and forms that lead from one to the other. This lets the second domain recognise the visitor as the same person within the same session. Where links are built by scripts, redirects or buttons that do not pass the parameter, we adjust them or add code to decorate the address. For embedded content, we use messages between the frame and the page or the tool’s built-in options. We install the same measurement property on every domain, through the tag manager where possible; see Google Tag Manager setup. We add unwanted referral exclusions for third parties such as payment providers, so that returning from them does not start a new session; see purchase and transaction tracking. We make sure consent settings apply across domains, so that a visitor’s choice on one site is respected on the next; see consent-aware analytics configuration. We test full journeys on desktop and mobile, in several browsers, including those that restrict cross-site cookies, and check that source and medium remain unchanged from the first domain to the final conversion. We compare conversion counts before and after, check ad platform reporting, and monitor for several weeks for edge cases such as redirects, in-app browsers and ad blockers; see advertising platform analytics. We document the set-up and add it to your launch checklist, so that new domains and tools do not break measurement. We cannot track users who block all analytics, and some browsers limit cookie life, but a correct set-up keeps credit with the real source.