Cookies24hours v2

ITP update: Cookies in Safari now expire after 24 hours. How big is the impact on my analytics data?

Millions of websites rely on Google Analytics, and the connection to Google Ads, to optimize their online marketing spend. It is critical for every online marketer to know the revenue each campaign delivered to continue to optimize channels, keywords and content. However, with the latest ITP developments in Safari, key data is now being lost. Initially, they announced to limit cookies to 7 days, but as of last month this has been reduced to 1 day. How much depends on your website and your target audience.

The struggle with ITP, or Intelligent Tracking Prevention, has intensified this year. Apple initially planned to limit the storage of cookies to 7 days. However, as the latest version of Safari, launched in October 2019, this now has been reduced to one day.

In this blog we shortly describe what is going on, and help you to estimate what the exact impact of ITP will be for your website and analytics data.


“With ITP 2.2 the expiry of persistent client-side cookies is 24 hours”

Introducing ITP, John Wilander, WebKit (Sep 23 2019)



What has that got to do with me as an online marketer?

To be honest, the impact is enormous. Not only will you start to experience a measurement error in your reported channels. On top of that, your efforts in SEA, marketing and channel optimization will also be harmed as the data you track if incomplete and incorrect.

How that is possible is best described by a practical case. Imagine, two users click on your Google search advertisement, and each executes a successful purchase a little over one day after clicking the ad.

  • For User A on Chrome  – without ITP –  you can easily attribute this sale to the ad(s) that the user previously clicked on. In GA this transaction will show up as Google/CPC.
  • For User B on Safari – with ITP –  a new user will be created after one day, meaning that you will not be able to attribute this sale to the ad attributing this channel as ‘none’ (or direct).

User A without ITP vs. User B with ITP 2.2+


In this practical case we have not been able to attribute the second transaction, meaning that in our report Google/CPC will only show the first transaction. Also, it will seem that the ad user B has seen will not have resulted in any transactions, thus giving you the impression that the first ad is performing better.

Translating this to your website analytics: Your Google Analytics reports will show transactions decline in areas with Google/CPC as Source/Medium. And to make matters even worse, you will start reporting a reduction in your return on marketing spend.

So the question begs, what will be the impact of ITP on your website once most of your Safari users have updated their browser?

So far, the impact has been limited to the latest Safari versions, which were launched during the last few months. However, as more users update their Safari (and iPhone), the impact will grow. So the question begs, what will be the impact of ITP on your website once most of your Safari users have updated their browser?

Well, that really depends on your specific target group, but we have compiled an easy 3-step guide to help you calculate the impact.

Step 1
Find the share of Safari in your transactions

  • Open Google Analytics and go to Audience > Technology > Browser & OS
  • Check in the conversion ‘eCommerce’ columns for Safari, what the % is of transactions is for Safari
View the Safari share in Google Analytics

Step 2
Figure out the share of transactions that come in after 1 day (as ITP 2.2 resets cookies after this time).

  • Select a time period prior to ITP, such as January 1st 2019 to May 1st 2019. 
  • Go to Conversions > Multi-Channel Funnels > Time Lag
  • Add the conversions that occur after 1 day (or check what occurs on 1 day and subtract that from 100%)
Select Time Lag in GA

Step 3
Multiply the result from step 1 and 2 and see what share of transactions you will not be able to allocate correctly. A calculation example could be:

  • You see 42% Safari users in Google Analytics (for January 1st 2019 to May 1st 2019)
  • You see 3.925 conversions that occur after 1 day in Google Analytics
  • The outcome: 0,42 x 3925 = 1.648 transactions that will probably not be correctly allocated


Previously, 18% of our traffic was ‘infected’, which directly resulted in more direct traffic.

Bruynzeel Keukens using TraceDock


So why didn’t I hear about this before?

As mentioned in the introduction, ITP is a feature that Apple added in Safari in October 2019. And even though Apple is very aggressive in their browser update, not all users have upgraded their desktop of iPhone yet. We expect a complete roll-out in the coming 4 months, which you can also see as a suitable timeline for you to find a good solution.


So, what now…

If the majority of your online spend is performance-based, hearing that you are going to miss out 10 to 30% transaction attribution is not something you like to hear.

Luckily there are solutions out there. According to the original ITP introduction, the recommended route is to set up a server-side solution for attribution and ad impression tracking on your website.

The way we see it, you can either implement a solution yourself or have a look at an out-of-the box solution like TraceDock. With TraceDock we provide an easy and well-tested solution that can be installed on your website within 20 minutes.

If you are curious to learn more, let us know and you can schedule in a 15-min online demo



Whatever you choose, we hope to inspire you to take action.
This is your cue as an online marketer to act and find a solution or see your marketing efforts decline.


Written by Harm Linssen
Partner at Relevant Online

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