A conversion is an action when a user interacts with an ad (clicks or views the ad) and then takes an action that the advertiser setup as valuable, such as an online purchase.
Modeled Conversions are created using historical data. Google states Modeled Conversions are based on aggregated and anonymized data to estimate conversions that Google is unable to observe directly. Modeled Conversions were first introduced in 2017 via Google Analytics.
Google says Modeled Conversions are inferred for browsers when there isn't direct conversion tracking information available. Modeled Conversions are a way to provide conversions to performance advertisers with ad impressions on browsers affected by ITP, or other protection tracking mechanisms.
Google introduced Modeled Conversions last month in DV360, and in July 2019 in Google Ads. When Modeled Conversions were introduced in Google Ads, Google announced Modeled Impressions enable advertisers to measure app installs and in-app conversion events from iOS browsers. Modeled Conversions aren’t available in third-party measurement tools.
In DV360, advertisers can opt-out for Modeled Conversions. Google states that in DV360, Modeled Conversions will result in a low double-digit increase in conversions for most advertisers. Modeled conversions will start to be included in DV360 Conversions after September 28.
There are no details on how the model works. Advertisers do not know what is the percentage of the modeled conversions.