Understanding Discrepancies in UTM Source Tracking
how come I have a user whose Initial utm source is X if this user doesn’t have any event where the utm source was X?
how come I have a user whose Initial utm source is X if this user doesn’t have any event where the utm source was X?
You're correct that, according to Mixpanel's documented behavior, the initial_utm_source property should reflect the first UTM source detected for a user—specifically, the UTM parameter present on the user's very first visit (page load) where UTM parameters are available. This value is then stored on the user profile and should correspond to an event where utm_source was X Web Attribution Track UTM Tags.If you are seeing an initial_utm_source value of X on a user profile, but there is no event for that user where utm_source is X, this is unexpected based on the official documentation. The knowledge sources do not provide an explanation for this scenario, nor do they mention any known bugs or edge cases that would cause this mismatch.Possible explanations (not confirmed in the documentation) could include: - The event with utm_source=X was deleted, failed to ingest, or is outside your current data retention window. - The initial_utm_source was set manually or via a server-side integration, which requires explicit property setting Sending Data to Mixpanel. - There is a data sync or integration issue, but this is not described in the knowledge sources.In summary: Based on the knowledge sources, it should not be possible for a user to have an initial_utm_source of X if there is no event where utm_source was X. If you are seeing this, it may require further investigation with Mixpanel support, as the documentation does not cover this scenario or provide a reason for such a discrepancy.
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Mixpanel sets the initial UTM properties (like initial_utm_source) based on the very first UTM parameters it detects when a user visits your site. These are stored as user profile properties and are intended to represent the user's original acquisition source. However, there are a few reasons why you might see a value for initial_utm_source (e.g., X) on a user profile, even if you can't find any event for that user where utm_source was X: 1. Initial UTM is set on first visit, not on every event: The initial_utm_source is captured from the first page load where UTM parameters are present and is then stored on the user profile. If the user’s subsequent events do not include utm_source=X (for example, if UTM parameters were only present on the very first page view and not on later events), you won’t see utm_source=X on those later events, but the initial_utm_source will remain set to X on the profile Web Attribution.2. UTM parameters may not be attached to all events: By default, UTM parameters are persisted as super properties and attached to all events, but this can be changed (e.g., by using stop_utm_persistence: true). If UTM persistence is disabled, only the event on the first page load will have the UTM parameters, and subsequent events will not, even though the initial_utm_source is still set on the profile Track UTM Tags.3. User identification timing: If a user is anonymous on their first visit (when the UTM parameter X is present) and only later gets identified (logs in or signs up), Mixpanel will associate the initial_utm_source from the anonymous session with the now-identified user profile. If you’re only looking at events after identification, you might not see any events with utm_source=X, but the initial_utm_source will still reflect the original anonymous visit Sending Data to Mixpanel.4. Events may have been deleted or not ingested: If the first event with utm_source=X was deleted, failed to send, or was filtered out, the initial_utm_source property could still be set if the profile update succeeded, but you wouldn’t see a corresponding event.
In summary, initial_utm_source is set based on the first detected UTM parameter, and it persists on the user profile even if subsequent events do not include that UTM value. This can lead to situations where the user profile shows an initial_utm_source that is not visible in the event stream, especially if UTM persistence is disabled or if you are only looking at a subset of the user's events Web Attribution, Track UTM Tags, Sending Data to Mixpanel.
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