What is ITP?
Intelligent Tracking Prevention (ITP) is the name of the tracking protection mechanism implemented in recent releases of Webkit, the open source browser engine used by Safari and others.
It’s stated intent is to eliminate cross-domain tracking which is used extensively by ad networks to track users across multiple websites and often abused.
Unfortunately, in targeting abusive use of cross site tracking the restrictions also impact the legitimate uses of cross-site tracking for things like single sign-on for organisations with multiple domains.
The Story So Far
There have been several iterations of ITP each with subtle changes in behaviour with regard to the way cookies are handled and each applying increasing levels of constraint on their use.
At the time of writing the latest version ITP 2.3 implemented in Safari on iOS 13 and on Safari 13 on macOS for Catalina, Mojave, and High Sierra.
One significant implication for Google Analytics is that Safari browsers now restrict the lifetime of the _ga cookie (used to identify individual users) from 2 years to just 7 days.
What Happens Next
While Apple has been leading the change in tightening browser security, other major browser vendors are quickly following with their own implementations.
The next release of Google Chrome (80), due for release in February, will incorporate significant ITP features which, given its market share, will impact a much wider audience.
To complicate matters, the different browser vendors are implementing ITP in subtly different ways and it is difficult to anticipate the effect on behaviour for a given web site.
A good reference for the current state of play is cookiestatus.com which offers a comprehensive summary of the tracking protection mechanisms implemented by the major browsers as well as some good background on the topic.
Simon Ahava’s article on ITP and its impact on Web Analytics provides an excellent overview.
For a perspective from the developers of Webkit see Intelligent Tracking Prevention (ITP) version 2.3 by John Wilander.
Another good article on ITP in relation to analytics is What Intelligent Tracking Prevention (ITP) 2.1 means for digital analytics by Tim Bennet
In a NutShell
To summarise then, if you rely on analytics to optimise your website, or you utilise cookies to provide a core service then you really need to be aware of ITP and its implications.