7 min.
Why the performance indicators you use will become unreliable
1L’art de la gestion de projet2Un projet à succès commence par une bonne gouvernance3Cascade, agilité, demandes de changement?

Why the performance indicators you use will become unreliable

Data Science & AI Marketing Analytics & Tracking

The challenge of the moment, with  the apocalypse of cookies , is to fully understand the repercussions of such a transformation in the digital world. Today, we are going to take a closer look at its consequences on the measurement of data, what we call  analytics . Get ready, you will have to question several performance indicators that you observe on a daily basis to measure your effectiveness!

We will therefore focus mainly on the repercussions of the cookie apocalypse on primary cookies. Unlike third-party cookies, which tend to disappear, primary cookies will remain relevant, but will experience major changes:

  • the lifetime of primary cookies will be limited to 7 days (or even 24 hours in some cases) on the Safari browser;
  • Cookies on Firefox will be deleted daily unless there has been user activity within 45 days.



What does this limited lifespan imply? In fact, this means that it will be difficult to recognize a user from one visit to another, which will have repercussions on two elements:

  • multi-channel attribution of your consumers' journey  across all of your digital marketing efforts and e-commerce activities in general;
  • direct (or 1:1) measurement  of overall performance on your Google or Adobe analytics platforms (i.e. post-click conversions).

Let's take an example: Isabelle arrives on the site www.monsite.com  from a Facebook ad, browses a bit, then leaves the site. She returns there nine days later in organic search to finally make a purchase there.

That's what happens in real life, but what about data collection?

  • Day 1: A user 123 is identified, a visit originating from a Facebook campaign is recorded. 
  • Day 9: A new user 456 is identified, a visit from organic search and a conversion is recorded.

The following data will therefore be counted in Google Analytics, depending on whether Isabelle uses the Google Chrome or Safari browser. 

Safari having its limits regarding the lifetime of primary cookies, this has an influence on the following indicators:

  • Number of unique visitors
  • Number of new visitors
  • Number of Assisted Conversions
  • Distribution of attributed direct conversions by channel.
  • Acquisition cost

You get the idea? Now ask yourself these questions when looking at the data:

  • Is the volume of new visitors real? You may not have acquired as many new users as you think.
  • Are the conversions attributed by channel representative of reality? A declining conversion rate does not necessarily indicate poorer performance!
  • Are your CPA and your ROAS representative of reality if you only observe them from the Google Analytics or Google Ads platform? On paper, costs do increase when looking at direct ( last click ) conversions and assisted conversions, but direct  last click conversions  alone remain the same.

These are reflections to integrate into your daily life before sharing any data related to the performance of your marketing activities. The cookie apocalypse is also affecting all content optimization and personalization activities. Your thoughts on A/B test results should also take this into account. You can also learn more by reading  the article  written by my colleague Nicolas Duval.



What to do in the short term?

  • In your reports, consider the margin of error of your analyzes based on the proportion of your traffic that comes from Safari and Firefox.
  • Avoid cross-referencing or comparing primary clicks or conversions data in Google or Adobe Analytics with that of your Adtech platforms, which depend on a third party. The margin of error will only increase. 
  • In Google or Adobe Analytics, consider the margin of error in customer journey analysis, based on the percentage of traffic coming from Safari and Firefox.  
  • Note that if you add UTM parameters in your campaigns, the lifetime of primary cookies in Safari will be 24 hours instead of 7 days.
  • Exclude the Safari browser from your testing experiences (A/B, MVT).

In the longer term, a lot of things are changing and falling into place. The watchword for 2021: adapt! Whether in terms of platforms, processes or people, we will have to be flexible to deal with this upheaval.



Google is developing a platform called GA4. With GA4, Google democratizes the analysis of large datasets with the integration of BigQuery. Companies will be able to export their GA4 data to BigQuery for free to perform advanced analyses, or even enrich their CRM data before pushing it to other platforms. To learn more about  4 good reasons to activate GA4 in 2021, it's here ! As far as we know, the new version will increasingly use machine learning to compensate for data gaps caused by the possible disappearance of cookies and IDFAs.

Another trend seen in the industry is the return to statistical inference models ( The Drum & Parker , 2020). More specifically, it is the return of one of the methods most used by marketers before the digital era:  marketing mix modeling  (MMM). Instead of analyzing the performance of digital media campaigns in silos, it's about analyzing the impact of all marketing activities on sales, both online and offline. As the organization matures from the point of view of data use, it is also possible to add other internal and external factors to have an even more complete view (weather, price indices competition, etc.).





To navigate this changing industry and enable reliable and robust modeling, it is necessary to properly integrate the tagging platforms to capture a maximum of data points that feed the models of the different platforms. 

In order to limit the loss of data captured by your media or  analytics platforms  on the client side (on the web page), "new" (or old 😉 ) methods for integrating pixels and other tracers are coming back into fashion: we are talking here about  server side tracking. Google Tag Manager now allows its server-side integration to enable new tracking methods that are more robust than those on the client side (Google, 2021). Please note that server-side tracing does not give you the right to override legal regulations in terms of managing user data. This type of integration will however prove necessary for a good number of organizations, both from the point of view of measurement and audience creation, because it will make it possible to play on the window of the limited lifespan. for primary cookies.

Finally, we can also maximize the collection of primary data by identifying users who have an online account. User data platforms (CDP) will be more and more interesting to exploit. It might therefore be wise to put efforts in place to build a solid user database.



Who says new platforms, new technologies and new processes also says training. Indeed, it will be essential to invest in the training of the people who are at the heart of your marketing activities in order to be able to continue to move forward with confidence in your next initiatives.

These people (you!) will first have to:

  1. fully understand the challenges of the cookie apocalypse to ensure that you control the use of current data;
  2. adapt as of today the actions which are posed on the marketing activities;
  3. think about the medium and long term strategies that could be put in place within the company – GA4, BigQuery, CDP, MMM and so on.



Perfect solutions do not exist, or at least not yet. On the other hand, it is important, above all, to understand the changes that affect measurement and to adapt our data analysis according to the new rules of the game. We must therefore constantly adapt and continue to show ingenuity to optimize our marketing tactics. 

We are currently experiencing great upheavals. This is a golden opportunity to get ahead and create a competitive advantage. Like what, even in the storm, it is possible to stand out.

Visit our special section dedicated to the Cookie Apocalypse to learn more about it