Why Do You See a Discrepancy in Conversion Tracking Results Between Facebook and Google Analytics?

As you probably know, you can track conversions using the tools within an ad platform, and you can also track conversions for the same campaigns using separate third-party analytics platforms like Google Analytics. But when you run ad campaigns on Facebook, you are very likely to encounter a big discrepancy between the number of conversions you see recorded by Facebook, and the number of conversions you see recorded by Google Analytics for the same exact campaigns.

But there are some very clear reasons for why this happens, and you should read the rest of this post to understand why that is.

The discrepancy between Google Analytics and Facebook Ads boils down to five big areas:

  1. Non-linear Conversions
  2. View Through Conversions
  3. Cross Device Conversions
  4. Dependency on Javascript
  5. Time of Conversion Difference

Below we are going to look at each of these five areas in detail.

  1. Non-linear conversions. First, Facebook tracks indirect non-linear conversions, meaning that if a user clicks your Facebook ad and views your site, leaves your site, then returns the next day and makes a purchase, Facebook attributes that conversion to Facebook. Google Analytics does not. Google Analytics is best at tracking direct last-click conversions — when a user clicks your Facebook ad, views your site, and converts right then and there without leaving.
  2. View Through Conversions. Second, Facebook conversion reports use a default 28-day window for click-through conversions and a one-day (24-hour) window for view-through conversions.  By uniquely tracking view-through conversions, Facebook takes credit for a conversion even if a Facebook user only sees your Facebook ad without clicking it, then visits your website and makes a purchase.  Furthermore, Facebook doesn’t differentiate between the two types of conversions: click-through conversions and view-through conversions are combined into a single data point for total conversions. Meanwhile, view-through conversion tracking is something Google Analytics can’t do for ANY type of campaign. Google Analytics records this conversion type as a direct source conversion, which means that, as far as Google Analytics is concerned, the same user typed your web address into their browser without being influenced by another campaign. (And tracking parameters like UTM codes can’t help you here, because those are directly tied to “clicks” and not “views.”) In other words, Google Analytics has no idea the user saw your Facebook ad.
  3. Cross Device Conversions. Facebook also tracks cross-device conversions (mobile to desktop, desktop to tablet, and so on) better than Google Analytics does. This is because whereas Google Analytics installs a single-location cookie to track a user’s activity on a single device, Facebook tracks activity using its Facebook user profiles (and the on-site Facebook Pixel).
  4. Dependence on Javascript. Google Analytics is entirely dependent on javascript within the browser, and people have the ability to turn off javascript, AND even if they don’t turn it off, javascript has a tendency to “fail” periodically.  There is no known solution to this, but Facebook does NOT have the same dependency, and therefore it will pick up conversions that are not recorded in Google Analytics when this happens.
  5. Time of Conversion Difference. Finally, Facebook records the conversion based on the time someone viewed the ad, and NOT the time that they completed the purchase, made the donation, or otherwise “converted.” So, if someone views/clicks the Facebook Ad on July 28, but converts on August 2nd, the conversion will be recorded as July 28th. Meanwhile, Google Analytics will record the conversion as August 2nd. This last reason should not impact the total number of conversions recorded for a campaign, but it will lead to a discrepancy in a given date range when you are analyzing results.

All five of these reasons help explain two things: (1) first, you are likely to see a big discrepancy when comparing your Facebook Ad campaign conversion data to your Google Analytics conversion data, and (2) secondly, the discrepancy is going to lean towards MORE conversions recorded in Facebook, and fewer recorded in Google Analytics.

But to be clear, it is still a smart move to track conversions using both systems, which is a best practice that we adhere to whenever possible — and doing so will result in better data for your campaigns, as long as you are aware of the “rules” that each conversion tracking system follows.

Dubravka Vasiljevic, Ad Platform Manager at the Will Marlow Agency, is a data-driven marketing professional with multiple Google Ad certifications. And she loves managing Google Grants

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