Google click identifier (GCLID) stops working in a handful of Google apps in iOS14
Google Click ID (GCLID) is a parameter passed in the URL with ad clicks, to identify the campaign and other attributes of the click associated with the ad for ad tracking and campaign attribution.
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.