PostHog’s cookieless mode uses a daily salt that changes—users appear as new people each day, making cross-session attribution impossible. That’s not a privacy advocate’s warning. That’s PostHog’s own documentation explaining what you lose when you go cookieless.

Cookieless tracking sounds like the privacy-friendly future. No consent banners. No cookie notices. No regulatory headaches. But for WooCommerce stores running paid ads, cookieless isn’t a solution—it’s data blindness dressed up as compliance.

What “Cookieless” Actually Means Technically#

Cookieless tracking tools don’t magically identify users without storing anything. They use hashing—combining IP address, user agent, and other browser signals into a temporary identifier. The privacy-preserving part? That hash changes daily.

PostHog explains it directly: “A hash is an irreversible function and a salt is a random value that changes daily which we delete once that day’s events have been processed.” Translation: the same customer visiting Monday and Tuesday is two different people in your analytics.

Matomo confirms the core limitation: “The most important downside of cookieless is reduced accuracy of unique visitor counts—you can only tell how many visits, not how many people make those visits.”

This isn’t a bug. It’s the entire point of cookieless tracking. Privacy means not recognizing users across sessions. But for ecommerce, not recognizing returning customers is business suicide.

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The Five Things Cookieless Tracking Destroys#

1. Returning Visitor Identification

With cookies: Sarah visits Monday, browses Tuesday, buys Friday. Your analytics shows one customer with a three-day journey ending in purchase.

Without cookies: Sarah appears as three separate new visitors. Each session is isolated. You have no idea it’s the same person, no journey data, no understanding of what brought her back.

Safari ITP already limits third-party cookies to 24 hours. Cookieless tracking extends that limitation to your own first-party data—every returning visitor beyond a day becomes invisible.

2. Purchase Attribution

The customer clicked your Facebook ad on Monday. They came back directly on Thursday and purchased. With cookies, you attribute that sale to Facebook—because you can connect the sessions.

Without cookies, the Thursday purchase has no connection to Monday’s ad click. Your Facebook attribution shows nothing. Your ROAS calculation is fiction.

InfoTrust states it plainly: “For anonymous GA property only hit-level data like total pageviews and events are accurately reported—session and user metrics are all inaccurate.”

3. Customer Journey Analysis

What pages do customers visit before purchasing? How many sessions does it take to convert? What’s the typical path from first visit to checkout?

Cookieless tracking can’t answer any of these questions. Every session is orphaned. You see isolated pageviews, never connected journeys. Funnel analysis becomes impossible because you can’t track the same user moving through stages.

4. Retargeting Audiences

Building audiences for retargeting requires recognizing users who visited but didn’t convert. Without cookies, you can’t identify those users. You can’t build “cart abandoners” or “viewed product but didn’t buy” segments.

Your ad platforms need user identifiers to retarget. Cookieless analytics provide aggregate data—total pageviews, referrer distribution—but nothing actionable for audience building.

5. Session Metrics

Bounce rate, session duration, pages per session—all meaningless without cookies. These metrics require knowing when sessions start and end for the same user. With daily hash rotation, you’re measuring individual page loads, not user behavior.

Simple Analytics explicitly limits itself to aggregate pageviews and referrers—no user paths, no cohorts, no advanced filters (Usercentrics, 2025). That’s not a feature gap. That’s the fundamental limitation of cookieless architecture.

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The Hash Collision Problem#

Cookieless tracking has another dirty secret: hash collisions. When two different users share similar IP addresses and browser configurations, they generate the same hash. The system counts them as one person.

PostHog documents this directly: “Hash collisions in cookieless tracking can cause two different users with same IP and browser to be counted as one.”

In an office building, coffee shop, or any shared network environment, multiple visitors might collapse into a single “user” in your analytics. You’re not just losing returning visitor data—you’re potentially undercounting unique visitors entirely.

When Cookieless Actually Works#

Here’s the thing: cookieless tracking isn’t universally bad. It works for specific use cases:

• Content sites measuring reach: If you only care about pageview totals and traffic sources, aggregate data is fine
• Privacy-first positioning: Some brands use “no cookies” as a marketing differentiator
• Minimal compliance requirements: Reducing consent burden for simple informational sites

But for WooCommerce stores—for any ecommerce business running paid acquisition—cookieless tracking removes the data you need to make profitable decisions.

You can’t optimize ad spend without attribution. You can’t improve conversion paths without journey data. You can’t calculate customer lifetime value without recognizing returning customers.

The First-Party Cookie Alternative#

The false choice is cookies versus no cookies. The actual choice is third-party tracking (dying) versus first-party tracking (thriving).

First-party cookies—set by your own domain with user consent—aren’t affected by Safari ITP or ad blockers the way third-party cookies are. They persist across sessions, enable returning visitor recognition, and support the attribution ecommerce requires.

Transmute Engine™ is a first-party Node.js server that runs on your subdomain (e.g., data.yourstore.com). It sets first-party cookies with proper consent, maintaining user identity across sessions while respecting privacy regulations. For users who don’t consent, WooCommerce order data (email, name) still enables conversion tracking through server-side events.

The result: privacy respect with business functionality. Not the false trade-off of cookieless tracking where you sacrifice both accuracy and actionability.

Key Takeaways#

• Cookieless tracking uses daily rotating hashes—the same user appears as a new visitor each day, breaking cross-session attribution
• PostHog, Matomo, and other tools document these limitations in their own documentation—this isn’t opinion, it’s technical reality
• Session metrics like bounce rate become meaningless without persistent user identification
• Hash collisions can undercount unique visitors when users share similar browser fingerprints
• Aggregate analytics work for content sites but fail for ecommerce requiring user-level attribution
• First-party cookies with consent remain the viable path for WooCommerce stores needing accurate tracking

Ready to track your WooCommerce store with data you can actually use? Explore first-party server-side tracking that respects privacy without sacrificing business intelligence.