initial_utm gets overwritten


We are experiencing the following behavior:

1) A user signups to our webapp with no utm_source on the URL parameters

2) Our webapp sends the Identify event without including the utm_source attribute

3) The identify event travels to segment and amplitude as expected.. and also as expected the initial_utm_source is empty.

Then... imagine 3 days later we send an email to that user including a remarketing campaign link. The link points to the signup and on the URL parameters we include utm_source=remarketingCampaign1

4) As expected, our webapp sends an identify event again to Segment and amplitude


Under this scenario we would expect the utm_source of the user to get written to remarketingCampaign1 and the intial_utm_source should have remained emtpy.

HOWEVER, what really heppened is that the initial_utm_source changed from epty to remarketingCampaign1.. making us think that the user made his initial signup from that campaign and that is not the case.


QUESTION: is this how it should really work? are we missing something?

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  • Maurizio Oneto thank you for writing in! Digging into the Amplitude docs, I believe this is the expected behavior on Amplitude's end. See the following link for reference

    Amplitude can capture the initial UTM parameters and referrer information for each user. The first-touch attribution values are set when a user's non-null UTM parameters are seen for the first time. The following user properties are set once:

    • initial_utm_source
    • initial_utm_medium
    • initial_utm_campaign
    • initial_utm_term
    • initial_utm_content
    • initial_referrer
    • initial_referring_domain
    • initial_gclid

    According to that information, the first time those values are seen, they will be forwarded to the initial fields in Amplitude.

    Hope this helps to clarify it!