Full Answer

Click identifiers are the linchpin of paid attribution: gclid tells Google which click led to a sale, and fbclid does the same for Meta. They arrive as URL parameters when someone clicks an ad, which feels durable but isn't. Safari treats them as cross-site link decoration and strips them on inbound navigation, and even when an ID survives the landing, ITP's short cookie lifetimes mean a browser often can't hold it across a multi-day purchase journey. So a browser-only setup loses exactly the clicks that converted slowly.

The defence is to grab the identifier the instant it arrives. An early server-side hook reads gclid, fbclid, and equivalents like ttclid from the request, then stores them server-side, tied to the session and copied onto the order at checkout. From that point the browser's behaviour is irrelevant, the ID is already on your infrastructure, beyond the reach of stripping or cookie expiry.

The payoff comes at conversion time. You send the stored click ID back to each platform through its server-side conversion API, Google's Data Manager/Ads API path and Meta's Conversions API, so the platform can credit the original click without depending on a third-party cookie. With Safari 26 enabling link-tracking parameter stripping for every user by default, this server capture is no longer an edge-case hardening step; it's the baseline for keeping paid attribution intact.