Introduction

Shopify says you made 400 sales.
Meta claims it drove 300 of them.
Google Ads takes credit for 280.
GA4 shows only 190.

Which one is right?

If you’ve ever tried to make budget decisions with these numbers on the table, you already know the answer: none of them — unless you unify the logic behind them.

This post shows how to build one clear source of truth that connects Shopify, Google Analytics 4 (GA4), and your ad platforms. So you can finally trust what’s working — and double down with confidence.

Why Every Platform Shows a Different Story

Each tool you use — GA4, Meta Ads Manager, Google Ads, even Shopify itself — uses a different attribution model.

That means they each decide for themselves who gets credit for a sale.

Here’s a quick breakdown:

• Meta Ads: Claims the win if someone clicked or viewed an ad within a certain time window (usually 7-day click or 1-day view).
  
• Google Ads: Attributes the sale to the last click — if it came from Google.
  
• Shopify: Credits the last non-direct click by default.
  
• GA4: Uses Data-Driven Attribution (DDA) — a model that looks at all touchpoints and splits credit accordingly.
  

Each system is technically right — according to its own rules. But if you compare them directly, you’re comparing different languages.

The result? Confusion, finger-pointing, and marketing decisions built on contradiction.

Why You Need a Single Source of Truth (And Why GA4 Wins)

To scale with confidence, you need one version of reality.

That doesn’t mean forcing every tool to agree — it means choosing one platform to anchor your decisions. At Kodanik, we use GA4 via Google Tag Manager (GTM) as the source of truth. Here’s why:

1. It sees the full journey
   GA4 tracks multiple sessions, touchpoints, and returning users — so it reflects how people actually shop.

    

2. It uses Data-Driven Attribution
   Unlike last-click models, GA4 splits credit across platforms — which shows the real contribution of each channel.

    

3. It’s customizable and testable
   With GTM, you control what data is sent, when, and how — with complete visibility.

    

4. It aligns revenue with real events
   GA4 can be configured to receive actual order values, transaction IDs, and source data — not just vague signals.

    

In short: it’s not biased. It’s consistent. And it can be rebuilt if something breaks.

If you want to understand how attribution models actually work across platforms, we break it down step-by-step in Ads Conversions Not Matching Shopify Sales.

The Core Components of Data Alignment

There’s no one-click solution for clean data. But there is a proven structure.

These are the four layers we build to unify Shopify, GA4, and ad platform data:

1. Purchase Event Fires Once — With Real Values

The first requirement is that your purchase event fires exactly once, and includes:

• Transaction ID (so events aren’t counted twice)
  
• Total value (the amount paid)
  
• Currency (to track real revenue, not estimates)

   

Without these fields, platforms can’t deduplicate conversions — and your reports become inflated or incomplete.

This mistake is more common than you’d think. If you’re seeing “weird” revenue numbers in GA4, start with Shopify GA4 Revenue Mismatch to fix the baseline.

2. UTM Parameters Persist Through Checkout

UTM parameters are tags added to your URLs that help identify where a customer came from. For example:

• utm_source=google
  
• utm_campaign=spring-launch

   

GA4 uses these to assign credit. But if Shopify drops those tags during the checkout process — which happens often — the final purchase gets attributed as “Direct.”

That breaks attribution, underreports ad performance, and makes campaigns look weak.

We solve this by storing UTMs in browser storage (like cookies) and passing them to GA4 at the moment of purchase.

3. Shopify’s Custom Pixel Connects to GTM

Many older setups relied on the now-deprecated checkout.liquid file to trigger purchase events. That method no longer works reliably.

Instead, we use Shopify’s Custom Pixel — a feature that lets you listen to ecommerce events like checkout_completed and forward clean data to GTM.

From there, GTM sends it to GA4 with all the necessary context — event name, order ID, revenue, currency, and UTMs.

This new setup is more stable, future-proof, and fully aligned with Shopify’s latest API structure.

If your tracking broke after a redesign, this is likely the root cause. We walk through the fix in Shopify Theme Change Broke Your Tracking?.

4. Attribution Windows Are Aligned

Every platform uses a different conversion window — the time between a click and a purchase that still counts as a “conversion.”

• Meta Ads: usually 7-day click / 1-day view
  
• Google Ads: varies, but defaults to last click
  
• GA4: customizable, often 30-day lookback

   

If your windows don’t match — or your model doesn’t reflect the customer journey — your attribution gets distorted.

In GA4, we adjust these windows and configure cross-channel rules to better reflect how people actually buy from your store.

The Payoff: Clean Reporting → Confident Scaling

Once this full structure is in place, you stop second-guessing every report.

• GA4 and Shopify match on revenue
  
• UTMs show which campaigns truly drove the sale
  
• Meta and Google Ads no longer double count
  
• Your ROAS becomes accurate across the board
  

(ROAS means Return on Ad Spend — how much revenue you generate for every dollar spent on ads. When calculated correctly, it tells you exactly where to scale.)

Clean tracking doesn’t just help your marketing team. It aligns founders, agencies, media buyers, and investors around one objective source of truth.

That’s what makes it scalable.

Conclusion

As long as every platform uses its own rules, your data will stay fractured.

Shopify shows sales. Ads claim credit. GA4 shows part of the picture.

To grow without fear, you need one consistent, testable, logic-driven system that reflects what’s actually happening.

That’s the source of truth.

Schedule a quick review call — we’ll audit your current setup, trace the gaps, and rebuild a reporting layer that makes every dollar traceable.