Tracking conversions from Facebook ads – things you need to know

Are you scratching your head, trying to work out why Facebook ad conversions don’t match up in Ads Manager and Google Analytics? Here are some reasons why…

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This month, when looking at the stats for a couple of clients’ sales for 2021, I noticed that there was a massive discrepancy between the purchases reported in Facebook Ads Manager and those reported from Facebook / CPC in Google Analytics.

If you’re experiencing the same issues, here are the things you need to consider.

How you track conversions from Facebook ads

There are two main ways to track purchases/conversions from Facebook ads; using the Facebook Pixel and adding Google’s UTM tracking code to the destination URLs of the ads for Google Analytics (GA).

When using these two methods for tracking conversions the results can be staggeringly different and these are some of the reasons why:

  1. Some of the ads may be missing the UTM tracking code. The UTM code has to be manually added as URL parameters and when you have a lot of campaigns and ads there could be some URLs that are not tagged correctly. This will obviously stop GA being able to attribute sales to those ads. facebook url parameters
  2. The Facebook pixel isn’t installed correctly. Some may find that GA reports more sales/conversions than Facebook Ads Manager and if this is the case then it could be that the pixel isn’t installed correctly. (Find information about how to create and install the pixel here.)
  3. The Facebook Pixel attributes sales differently to Google Analytics. Facebook says: “When someone visits your website and takes an action (for example, buying something), the Facebook pixel is triggered and reports this action. This way, you’ll know when a customer took an action after seeing your Facebook ad.” This means that a click doesn’t have to happen for Facebook to take credit for a sale, whereas Google Analytics does.
  4. How Facebook and Google Analytics track people is different. While GA uses first party cookies (which can be disabled), Facebook doesn’t need to. This is because you have to be logged into Facebook to see the ads and that therefore makes it very easy for them to track people across devices and also throughout time too. This means Facebook knows if you saw an ad on their mobile app on Tuesday and then went onto your tablet and did a Google search for that brand and purchased something on the following Friday (as long as you are signed into Facebook on the tablet too, which most people are).

Which conversion figure should you trust?

The truth is that both are very important to look at (if everything is implemented correctly). Whilst Google Analytics shows you the number of conversions that have come as a direct click through from an ad, Facebook Ads shows the figure that has been influenced by your ads in some way.

Even if the user didn’t click on your ad there and then, the likelihood is that they’ve seen your branding and that has influenced their purchase/enquiry later down the line.

How does the recent iSO 14.5 update impact things?

Back in April 2021 Apple released the iSO 14.5 update which had a big impact on the way that Facebook can receive and process conversion events via its pixel. This consequently means that “businesses that advertise mobile apps, as well as those that optimize, target, and report on web conversion events from any of our business tools may be affected.”

“Apple’s policy prohibits certain data collection and sharing unless people opt into tracking on iOS 14.5 or later devices via the prompt. As a result, ads personalization and performance reporting may be limited for both app and web conversion events.”

However, Facebook says, “In response to these changes, we are processing pixel conversion events and app events from iOS 14.5 or later devices using Aggregated Event Measurement. This will help support your efforts to preserve user privacy and help you run effective campaigns.”

So while this update will have affected conversions being tracked by the pixel, Facebook is trying to ease the pain by introducing its Aggregated Events. “Facebook’s Aggregated Event Measurement is a protocol that allows for measurement of web and app events from people using iOS 14.5 or later devices. Aggregated Event Measurement limits domains and mobile apps to 8 conversion events that can be configured and prioritized for Aggregated Event Measurement reporting.” Now for some advertisers only being allowed eight conversion events per domain will be horrendous but hopefully for most, like those trying to track simple things like, Add to Cart, Purchases etc. it should help.

To find out more about Facebook’s Aggregated Event Measurement click here.


The truth is that there is always going to be something that could affect the tracking of conversions. All we can do is try and ensure that everything is implemented correctly so that we are using the most accurate data possible and optimise campaigns accordingly.

If you’d like help with your Facebook ad management please get in touch.

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