Facebook Analytics vs Google Analytics: Why are the conversion numbers different

As Digital Marketers, we are always looking for the best information to show us how well our campaigns are running across all channels. However, you may have noticed that Facebook and Google don’t seem to be on the same wavelength.

Businesses rely on critical metrics such as Cost per Acquisition (CPA) and Return on Investment (ROI) to justify campaign spend and show the successes and failures of campaigns. But, if you have ever created any form of Facebook advertising that optimises conversions, you’ll see that Facebook displays a much higher number than Google Analytics does.

So what is going on here, and why is there such a drastic difference?

Tracking: people-based vs cookie based

First, the session count (the number of times a user visits your website) should always be the same on Facebook and Google. The discrepancies occur when we begin to look at attribution, conversions and measuring - both platforms will correlate over the same period of time, however, Google Analytics will not give credit for converting to Facebook on their platform due to the difference in conversion tracking.

Conversion tracking:

Google uses cookie-based tracking with ‘last click’ attribution modelling. In this model, the conversion is given to the channel the user used last to come to the site (e.g. Organic, Direct, Social)

Facebook uses people-based tracking with a 7-days click & 1-day view lookback conversion window (this used to be a 28-days click & 1-day view until the recent updates from iOS 14). Under this model, conversions that occur within seven days of clicking an advert will be attributed to the campaign.

Measuring: all for one vs one for all

Google and Facebook are trying to show different things in their analytics. Facebook isn’t a multi-channel platform so it is not trying to track the traffic or conversions from other channels. Over a seven-day lookback period, all conversions will be attributed to Facebook if they are part of the conversion funnel at any point.

On the other hand, Google Analytics is trying to give you a complete overview of traffic to your site and the channels performing best.

Here is an example of a customer journey:

  1. The user initially clicks through to your website through a Facebook Advert on their mobile phone
  2. The next day the same user goes directly to the site on their desktop computer and takes time to learn more about the particular service or product
  3. Finally, they return to the site through an Organic Search (general search not influenced by paid advertising) on their laptop device and make the purchase.

With Facebook being part of the journey, it would be attributed to the advert on their platform. Google would attribute it to Organic Search as that was the last channel the user came to the site through and converted on.


Currently, Google does not track conversions across multiple devices unless the users are signed into Chrome. It is estimated that 49% of UK online consumers use Chrome as their browser of choice. Assuming that all of these are signed in to Chrome (which they won’t be), that leaves 51% who can’t be tracked between devices.

Another thing to mention is in-app browsers. Social networks like Facebook use in-app browsers to keep people on their app - which don’t have the same information as the standard browser nor are they supported in Chrome.

On the other hand, Facebook is much better at tracking across multiple devices as it uses people-based tracking (ID to track associated data with the user). Allowing Facebook to track that the advert played a part in the purchase.

Impression based conversions

Facebook can attribute conversions based on a person looking at the advert on their app. This means that if a person sees the advert on Facebook and then uses their browser to go to the site and purchase rather than click the advert, Facebook will assume the advert played a part in the purchase. Google is unable to attribute based on someone viewing an advert, so unable to provide a conversion.

All of this is very technical stuff, but how do we make sure we are getting the best information possible to instruct us for future actions. In truth: we recommend both! Now, many reading this will have groaned at this statement. The reason I know this is because I did the same thing when I learned this.

Google is excellent at giving you an overview of all channels on your site. But you also need to know that your Facebook campaigns are working to build brand recognition through its impression-based conversions and cross-device tracking.

Written by Bailey.

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