The source – support.google.com
Google Merchant Center has implemented support for additional sources to track free conversions using an automatic tag.
Auto-tagging is a feature that allows you to use third-party web analytics tools. How it works: When a user clicks on a free offer, a unique identifier is automatically added to the URL.
You can now use this feature to view conversions for all impressions on Google's free search offers, including local ones.
Additional conversion data from free offers in organic and local delivery will be included in the reports automatically. That is, those who already use the function do not need to do anything additional. Others can activate it in their Merchant Center account by setting the switch to the appropriate position.