Safari holds 24% of browser market share. Every one of those visitors has a 7-day maximum cookie lifetime—and just 24 hours if they came from a Facebook or Google ad. That’s one in four visitors whose attribution your current tracking setup is losing.

Chrome allows cookies to persist for 400 days. Safari caps JavaScript-set cookies to 7 days, or 24 hours when tracking parameters like fbclid or gclid appear in the URL. The gap isn’t subtle. It’s the difference between tracking a customer journey and guessing at it.

How Safari ITP Breaks Your Attribution

Intelligent Tracking Prevention launched in Safari back in 2017. Since ITP 2.2 in 2019, Apple has systematically restricted how cookies work in their browser. The rules are straightforward but devastating for WordPress store owners.

JavaScript-set cookies expire after 7 days of user inactivity. Your analytics cookie, your user identification cookie, your cart memory—all gone after a week if the visitor doesn’t return.

But here’s where it gets worse for paid advertising: when Safari detects tracking parameters like fbclid or gclid in your URL, it reduces that 7-day limit to 24 hours. A customer clicks your Facebook ad on Monday. Browses your store. Leaves without buying. Returns Tuesday afternoon and completes their purchase. In your attribution? That conversion shows as direct traffic—new visitor, no campaign source, no attribution.

Your highest-value traffic—paid ad clicks—gets the shortest cookie life.

The Scale of the Problem

Safari’s 24% market share means roughly one in four visitors to your WordPress store experiences these restrictions. But it’s not evenly distributed. iOS dominates mobile, and all iOS browsers use Safari’s WebKit engine under Apple policy. Chrome on iPhone isn’t really Chrome—it’s Safari in disguise, inheriting every ITP restriction.

You may be interested in: Server-Side Cookie Setting: Why Your Server Can Set Cookies That Safari Cannot Kill

Remarketing audience size gets reduced to a 7-day window for Safari users (Stape, 2025). If your retargeting campaigns assume 30-day or 90-day audiences, you’re missing everyone on Safari who visited more than a week ago.

The math compounds quickly. If 24% of your traffic uses Safari and your average time-to-purchase spans 10+ days, you’re systematically under-attributing conversions that started with your marketing but completed outside the cookie window.

What Server-Set Cookies Actually Fix

Here’s the technical distinction that matters: Safari ITP targets JavaScript-set cookies. Cookies set via HTTP Set-Cookie headers from your own server can persist up to 400 days—but only under specific conditions.

The server setting the cookie must share the same IP address as your main website (Safari 16.4+ rule). Third-party servers, even with CNAME cloaking, get detected and restricted. But a true first-party server on your subdomain—like data.yourstore.com pointing to your own infrastructure—can set cookies that survive ITP.

Translation: server-side tracking from your own subdomain bypasses Safari’s JavaScript cookie restrictions.

This is why first-party architecture matters. Standard client-side tracking uses JavaScript to set cookies in the browser. Safari sees that and applies ITP restrictions. Server-side tracking from your own domain uses HTTP headers to set cookies—a different technical path that ITP doesn’t restrict the same way.

The Practical Implementation

Getting server-set cookies that bypass ITP requires three things: a first-party subdomain, server infrastructure that matches your website’s IP, and tracking that runs server-side rather than client-side.

You may be interested in: User Identification Without Cookies: The 4 Methods WooCommerce Stores Actually Have

Transmute Engine™ is a first-party Node.js server that runs on your subdomain (e.g., data.yourstore.com). The inPIPE WordPress plugin captures events from WooCommerce and sends them via API to your Transmute Engine server. Because it runs on your infrastructure with matching IP, cookies set by this server persist beyond Safari’s JavaScript restrictions.

This matters for attribution because you maintain user identity across sessions—even on Safari. A visitor who clicks your Facebook ad can be identified when they return 10 days later because their server-set cookie persists where a JavaScript cookie would have expired.

Beyond Cookies: The Redundant Approach

Smart attribution in 2026 doesn’t rely on any single identification method. WooCommerce stores have multiple options: first-party server-set cookies, WordPress user IDs for logged-in customers, hashed email addresses at checkout, and complete order data for conversion matching.

The store that tracks Safari visitors in 2026 uses all available methods—not just JavaScript cookies that ITP kills.

Facebook CAPI and Google Enhanced Conversions accept hashed customer data directly from your server. When a customer completes an order, you have their email, phone, and address—enough for conversion matching without any cookie at all. Safari’s ITP doesn’t affect server-to-server data transmission.

Key Takeaways

• 24% of your traffic is affected: Safari users have 7-day cookies maximum (24 hours from paid ads)
• JavaScript cookies are the target: Server-set cookies via HTTP headers from same-origin can bypass ITP
• First-party infrastructure matters: Your tracking server must share IP with your main site
• Paid ads hit hardest: URLs with fbclid or gclid reduce cookie life to 24 hours
• Multiple identification methods: Don’t rely solely on cookies—use email hashes and order data for conversion matching

Ready to fix Safari attribution? Learn how first-party server-side tracking works at seresa.io.