Intelligent Tracking Prevention (ITP)

What is Intelligent Tracking Prevention?

Intelligent Tracking Prevention (ITP) is a privacy technology in Apple's WebKit browser engine — the foundation of Safari on macOS, iOS, and iPadOS. First introduced in 2017, ITP uses machine learning classifiers and hard-coded rules to identify and restrict tracking behavior. Its goal is to prevent companies from building cross-site user profiles without consent.

ITP has gone through multiple major iterations, each tightening restrictions. In its current form, ITP blocks all third-party cookies by default, caps client-side (JavaScript-set) first-party cookies at 7 days, and applies further restrictions to cookies set via tracking-classified domains — including a 24-hour expiration for cookies set by JavaScript on pages reached through a cross-site navigation with query parameters or fragments.

Why it matters

Safari holds approximately 18-20% of global browser market share, but that figure understates ITP's impact. In key markets like the United States, Safari's share exceeds 30%, and on mobile devices it often surpasses 50%. For e-commerce and direct-to-consumer brands, a significant share of traffic and revenue flows through Safari.

ITP's restrictions create concrete problems for marketing teams:

• Identity loss — A JavaScript-set analytics cookie that expires in 7 days means any visitor who returns after a week looks like a brand-new user. Returning customer rates appear artificially low.
• Attribution collapse — If a user clicks an ad on Monday and converts on the following Wednesday, the cookie linking those events may already be gone. The conversion appears organic, and the ad campaign looks underperforming.
• Audience shrinkage — Retargeting lists built from Safari visitors decay rapidly, reducing the pool of addressable users within days.
• Revenue misattribution — When roughly a third of your traffic cannot be tracked beyond 7 days, attribution models systematically undervalue upper-funnel campaigns with longer consideration cycles.

How ITP works

ITP applies restrictions at multiple layers:

1. Third-party cookie blocking — All cookies from cross-site (third-party) contexts are blocked entirely. Ad pixels and tracking tags from external domains cannot set or read cookies.
2. Client-side cookie capping — Cookies set via document.cookie (JavaScript) on the first-party domain are capped at a 7-day expiration, regardless of what the script specifies.
3. Decorated link detection — When a user arrives from a classified tracking domain via a link containing query parameters or fragment identifiers (e.g., ?fbclid=...), JavaScript-set cookies are further restricted to a 24-hour lifespan.
4. Website data isolation — After 30 days without user interaction, Safari can purge all stored data (cookies, localStorage, IndexedDB) for that domain entirely.

ITP restrictions summary

The last row is critical: server-set first-party cookies delivered via an HTTP Set-Cookie header from a first-party subdomain are not restricted by ITP. This distinction is the foundation of every durable tracking strategy on Safari.

How Ingest Labs handles ITP

Ingest Labs sidesteps ITP entirely by setting its identity cookie (MPID) server-side via an HTTP response header from a subdomain on the customer's own domain. Because this is a genuine server-set first-party cookie — not JavaScript-set and not from a third-party domain — Safari's ITP rules do not apply. The MPID persists for approximately two years, giving marketing teams continuous identity resolution on Safari without any data loss from the 7-day or 24-hour caps that affect client-side tracking solutions.