Intelligent Tracking Prevention 2.3: The neverending ITP story

Alistair Johnstone

Data & Analytics Consultant

What is Intelligent Tracking Prevention?

Intelligent Tracking Prevention (ITP) aims to prevent cross-site user tracking, stopping cookies from following searchers around the web. It’s been around since 2017, but it’s a cat and mouse game – when new ways are dreamt up to circumvent the technology, ITP evolves to prevent them.

Read about how to measure the impact of ITP 2.x on your business.

What’s changed in the latest update?

Since the beginning, ad tech companies have attempted to bypass ITP restrictions in various ways to track browsing behaviour. The latest version of ITP (2.3) prevents some of the most recent cookie workarounds.

Here’s a quick overview of the workarounds and how ITP 2.3 tackles them…

Alternative first-party storage

The workaround

To bypass ITP’s cookie restrictions, alternate first-party browser storage methods, like localStorage, have been used instead. This allows cross-site tracking by storing unique identifiers in the user’s browser storage. 

ITP’s solution

As it does with cookies, ITP now caps the lifetime of all script-writable website data – like localStorage – after a navigation with link decoration (a link containing URL parameters that are used to identify users) from a classified domain.

Using the document.referrer

The workaround

ITP already has measures in place to prevent tracking via link decoration, however, instead of decorating the link on the destination page, researchers discovered people were decorating the referrer URL and then reading the referrer on the destination page using JavaScript. 

ITP’s solution

ITP has downgraded ‘document.referrer’ to the referrer’s effective top-level domain (eTLD+1) after a navigation from a classified domain. This will prevent unique identifiers being communicated in this way.

What next?

It’ll be interesting to see what the ad tech companies come up with next. But we can certainly expect more cat and mouse maneuvers: ITP workarounds, fixes to ITP workarounds, more ITP workarounds…

Want help with your web analytics? Please email us at results@icrossing.co.uk.

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