Google this week announced that will no longer send the Google click identifier (GCLID) for traffic coming from ads on a handful of Google apps. The lack of GCLID is due to the Apple’s release of the App Tracking Transparency (ATT), in iOS 14.5 update.
According to Google, the &gclid={GCLID} will not be appended to ad clicks and the {gclid} ValueTrack parameter will be set to empty text “”, so advertisers will see a decrease in reported website conversions, and a decrease in reported offline conversions (imported from clicks).
Google is recommending advertisers to implement the global site tag (gtag.js), Google Tag Manager (gtm.js), where a Google Analytics property is linked to a Google Ads account, Google Analytics (analytics.js) will set a new first-party cookie on your domains by default.
The first-party cookie can attribute conversions back to ads subject to ATT policies.