Google Consent Mode and dropout in users and sessions

This article is for website or app owners who are concerned about missing data from users after installing Google Consent Mode v2.

Written by NelsonLast update 3 months ago

This article is for website or app owners who use a cookie consent banner or another consent management solution and, after installing Google Consent Mode v2, see traffic drop in sessions and users who opt out.

When you implement a consent banner for your website or app, Google Analytics 4 will be missing data for users who decline consent. Google Analytics 4 (GA4) will use behavioral modeling and machine learning to model the behavior of users who decline analytics cookies based on the behavior of similar users who accept analytics cookies. In behavioral modeling, there are Modeled data or Observed data for reporting user and session metrics.

When users visit your website or app and grant consent for analytics cookies or when they don't opt out of personalization using advertising ID, Google Analytics associates user behavior with various identifiers to provide continuity in measurement. This data is called observed data and is the most reliable.

When users don't grant user consent, events are not associated with a persistent user identifier. The data will be missing for users who decline consent. In this case, behavioral modeling for consent mode will be used to get modeled data. Behavioral modeling for consent mode uses machine learning to model the behavior of users who decline analytics cookies based on the behavior of similar users who accept analytics cookies.

Because the model is trained on the observed data for your GA4 property, your property must have enough data to train the model.

To be eligible for behavioral modeling, your property must meet the following prerequisites:

Google Consent Mode v2 is enabled across all pages of your websites and all app screens of your apps.
Google Consent Mode v2 for web pages must be implemented so that tags are loaded before the consent dialog appears, and Google tags load in all cases, not only if the user consents (in the case of advanced implementation).
Your website or app collects at least 1000 events per day with analytics_storage='denied' for at least 7 days.
The property has at least 1000 daily users sending events with analytics_storage='granted' for at least 7 of the previous 28 days. When you have a few users, it may take more than 7 days to meet the data threshold within those 28 days to train the model successfully.

In conclusion, if you have recently implemented Google Consent Mode v2 correctly and are still concerned about missing data from users who opt out, it could be due to a lack of users for Google modeling of rejected users. It needs some time and a number of users per day to model the data. In this case, your GA4 session metrics should improve over time.