This discrepancy between the referring domain and UTM parameters is a common issue in web analytics and can occur due to several reasons. Let's explore the possible causes based on the information provided in the Mixpanel documentation.
1. Initial vs. Current Referrer:
Mixpanel tracks both initial and current referrer information. The discrepancy you're seeing might be due to the difference between these two types of referrer data. As mentioned in the [Traffic Attribution: Analyze your marketing channels](https://docs.mixpanel.com/docs/tracking-best-practices/traffic-attribution#web-attribution) documentation:
"Mixpanel's Javascript library will track Initial Referrer and Initial Referring Domain and append them as a property to any event that a user completes. These properties are stored in the Mixpanel cookie the first time a user comes to your site and will not change on future site visits as long as the cookie is not cleared."
This means that the referring domain you're seeing (Google) might be the initial referrer, while the UTM parameters (Facebook_Mobile_Feed) represent a more recent interaction.
2. UTM Parameter Persistence:
By default, Mixpanel persists UTM parameters across events as Super Properties. This can lead to situations where the UTM parameters don't match the current referring domain. As stated in the documentation:
"UTM parameters are by default persisted across events as Super Properties. To opt in to the recommended modern behavior most compatible with our attribution models, use the SDK initialization option {stop_utm_persistence: true} to disable UTM param persistence."
3. Multi-touch User Journey:
The user might have initially come from Google, but later clicked on a Facebook ad. The referring domain could be from the initial visit, while the UTM parameters reflect the most recent interaction.
4. Third-party Redirects:
Some ad platforms use redirect chains that can obscure the original source. The user might have clicked a Facebook ad that redirected through Google before reaching your site.
5. Browser Security Settings:
As mentioned in the documentation:
"The user may have typed the website address directly, clicked a bookmark, clicked a link from an email, or might have security settings in their browser that prevent referrer data from being passed."
This could result in Google appearing as the referrer even when the traffic actually came from a Facebook ad.
To address this issue and improve your attribution accuracy, consider the following steps:
1. Use the {stop_utm_persistence: true} option when initializing the Mixpanel SDK to ensure UTM parameters are not persisted across sessions.
2. Implement a custom attribution model that takes into account both the referring domain and UTM parameters, prioritizing the most recent or relevant data.
