• Context: We are investigating a data discrepancy between number of clicks in Google Ads and sessions in Google analytics (3000 clicks but only 500 sessions). We are using the standard Google Analytics "Global Site Tag (gtag.js)" snippet on the landing pages. There are additional trackers being used as well (facebook, twitter, etc.)

  • Test performed: Tester clicks on Google Ad in Google search results and performs a conversion action (signup). We look at a segment which shows this particular action (filter on country / city)

  • We observe different (source / medium) attributions, depending on which report we look at.

  • In "Behavior > Events > Top Events" we see source / medium as (l.facebook.com / referral) which I think is incorrect, since tester was coming from the Google search results page, not from facebook

enter image description here - In "Acquisition > Campaigns > All Campaigns" we see source / medium as (google / cpc), which I would consider to be more correct since the tester clicked on the advertisement on the Google search results page.

enter image description here

It appears that one session could have multiple (source / medium) attributions, is that correct, and could someone explain how this works? Are there different (source / medium) attributions depending on the filter?

  • Source/Medium should be independent of which report you're viewing. When you hover over the yellow shield next to the Top Events report title, what does it tell you?
    – Reve
    Commented May 19, 2020 at 14:33
  • hovering over the shield gives: "This report is based on 100% of sessions. Learn more The table rows have been filtered to include only data for "Event Category". The graph and table headers include totals for all data. Part of this date range occurs before the new users metric had been calculated, so the old users metric is displayed."
    – tassel3470
    Commented May 20, 2020 at 4:10
  • Okay, that's what I expected, but good to check. Thank you!
    – Reve
    Commented May 20, 2020 at 14:46

1 Answer 1


It looks like a new session is being started in the midst of this process. You can check in the Acquisition > Overview report (or in the segment builder) how many sessions are included in your location segment; I'm guessing it's at least 2.

Only sessions with associated campaign data will show in the Acquisition > Campaigns > All Campaigns report, so the Facebook referral would never show there, with or without filters or segments applied.

To determine how a new session is starting would require more information, but I would check on two things: If Facebook is involved in the process, such as with a "log in via Facebook" functionality, make sure that isn't triggering a new session. And check internal links along the way for inappropriate UTM parameters.

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