Why your tracking data has gaps

The five causes below explain most of the data gap in Shopware and Shopify stores today. The sections go through them in turn.

What does Safari do to your data?

For most stores, Safari is the single biggest cause of data loss, because iPhone users have above-average purchasing power in many product categories. Apple has restricted tracking step by step since 2017:

• Intelligent Tracking Prevention (ITP): Cookies set by JavaScript in the browser are deleted by Safari after seven days at most, in some cases after 24 hours. If a visitor returns after eight days and buys, your tracking sees a new user, and the original ad gets no credit.

• Advanced Fingerprinting Protection: Since iOS 26 and macOS 26, this protection is active by default in Safari for all browsing, not just private mode. Scripts that Apple classifies as fingerprinting receive less information.

• Link Tracking Protection: Removes click IDs such as gclid or fbclid from links. According to Apple's documentation, this applies by default in Mail, Messages and private browsing; in normal browsing only if users enable advanced protection for all browsing. Many articles claim more than Apple documents.

How many visitors use an ad blocker?

Ad blockers are more widespread in Germany than in most other countries. Surveys based on DataReportal and Statista put the share of internet users in Germany who use an ad blocker at around 39 percent. Not every ad blocker also blocks tracking, but the common filter lists reliably block requests to google-analytics.com, googletagmanager.com or connect.facebook.net. On top of that come browsers such as Brave and Firefox's tracking protection.

What does declined consent cost?

If a visitor declines marketing and analytics cookies in the cookie banner, no marketing tracking may take place for them. Server-side tracking cannot and should not close this gap. How large it is depends on your audience and the design of the banner. Two things can still be influenced: a banner that asks clearly and without tricks, and a setup that transmits all data completely for every consent that is given. What the law says and what role Google Consent Mode plays is covered in Chapter 3.

What technical breaks occur in the store?

Even when a visitor consents, not every event arrives. Browser-based tracking depends on every script loading on time and running without errors:

• Loading errors and drop-offs: If a visitor closes the page before a script has loaded, the event is lost.

• Redirects via payment providers: PayPal, Klarna and others take the customer through external pages and back to the store. Without a referral exclusion, this breaks the session, and the purchase is credited to the payment provider or not measured at all.

• Faulty integrations: Plugins, apps and theme changes that lose events after updates or send them twice.

What has the Shopify checkout overhaul changed?

Since 26 August 2026, Shopify no longer runs legacy scripts on the Thank you page and the Order status page, including on the Basic, Shopify and Advanced plans. Stores whose purchase tracking still relied on these scripts have been missing part of their orders ever since. How tracking works there today is covered in Chapter 8.

And the end of third-party cookies in Chrome?

That is not a cause, and it is important to say so honestly. For years, server-side tracking was sold on the back of the imminent end of third-party cookies in Chrome. It never came. In October 2025, Google retired the Privacy Sandbox technologies that were meant to replace them, and third-party cookies remain in Chrome with no shutdown date. Safari, Firefox and Brave block them anyway, and for tracking in your own store, first-party data is what matters.

What does this mean for your ad campaigns?

Google Ads, Meta and other platforms now set their bids almost entirely automatically. The algorithm learns from the conversions it is told about. If some are missing, it underestimates the campaigns that perform well and shifts budget in the wrong direction. So this is not just a reporting problem but a steering problem. How server-side tracking addresses it is covered in Chapter 2.