First-party cookies may already be getting blocked without you realizing it. Apple’s Intelligent Tracking Prevention has evolved from blocking obvious third-party trackers to limiting even first-party cookies when Safari’s machine learning model determines they’re being used for cross-site tracking.
Intelligent Tracking Prevention is a feature developed by WebKit, the engine used in Safari and other browsers, that reduces cross-site tracking by limiting cookies and other website data. It was designed to recognize and prevent domains with tracking capabilities from following users across the web, even when those domains use first-party cookies in technically compliant ways.
How ITP operates
Intelligent Tracking Prevention incorporates a machine learning model based on statistics collected by the browser. This classifier evaluates which domains can track users’ actions across different websites by analyzing patterns in how cookies are set, how redirects are structured, and how domains interact across sites.
If the machine learning classifier identifies that a particular first-party cookie can be used for cross-site tracking, the cookie faces restrictions. For some tracking patterns, cookies are limited to seven days of storage. For others, they’re deleted within 24 hours. In some cases, cookies are blocked entirely unless you use the Storage Access API to explicitly ask users for permission.
Impact on analytics implementation
The practical impact depends on how you’ve implemented tracking. Server-side analytics implementations using first-party cookies for legitimate site analytics typically aren’t affected. Client-side tracking that relies on URL parameters to pass data between domains often triggers ITP restrictions.
Common scenarios that trigger ITP:
- Using link decoration parameters (like click IDs) passed between domains
- Implementing cross-domain tracking through redirects
- Using first-party cookies set by third-party scripts
- Tracking users through multiple subdomains in ways that resemble cross-site tracking
Identifying ITP impact
Look for these indicators in your analytics: shortened session durations that don’t match user behavior patterns, attribution breaking for multi-session conversions (especially those spanning more than 7 days), and sudden drops in Safari traffic or conversion rates specifically from Safari users.
If you’re seeing these patterns, you’re likely hitting ITP restrictions. The solution typically involves moving to server-side tracking, adjusting how you handle cross-domain measurement, or reconsidering which metrics you can reliably track.
Read more about ITP and cookies on the Piwik PRO blog:
