The data layer problem killing your attribution.

The data layer problem killing your attribution.

Affiliate marketers and performance teams obsess over last-click attribution while their data layer is silently corrupted. Here's what's actually going wrong.

The most common issue: UTM parameters being stripped or overwritten mid-funnel. A user clicks your ad with utm_source=facebook, lands on your site, gets redirected through your affiliate tracking link, and arrives at the offer with the UTM data gone.

Fix: use server-side click ID passing (Facebook's fbc, Google's gclid) instead of relying solely on UTMs. These are harder to strip and survive redirect chains better.

Second most common issue: event firing order in GA4. If your "conversion" event fires before your "page view" event due to async loading, your session data is incomplete and attribution looks wrong.

Third: cross-domain tracking breaks when a user moves from your landing page to your checkout page on a different subdomain. GA4 requires explicit cross-domain configuration or you'll see direct traffic spikes that are actually attributed visits.

Fix the data layer before optimizing campaigns. You can't optimize what you can't measure accurately.