Hi digital marketers, this is Faisal Amin. In this 2026 updated guide, I show you exactly how I set up GA4 eCommerce tracking on a Shopify store using Google Tag Manager, based on a theme-independent data layer. I start from the basics: collecting the GA4 Measurement ID from the GA4 Admin → Data Streams, then creating a constant variable in GTM so I can reuse the same ID across every event tag without mistakes. Then I build the full Shopify funnel tracking step by step: page_view, view_item, add_to_cart, begin_checkout, and purchase. For Shopify, I don’t rely on “automatic” parameters—I send page_title, page_location, and page_referrer with every event because that makes GA4 reporting clean and consistent. For product events, I follow Google’s recommended parameters like currency, value, and items, and I show how I pass the items array using a custom JavaScript variable so GA4 receives item_id, item_name, price, category, and quantity correctly. Finally, I test everything properly using GTM Preview/Tag Assistant and GA4 DebugView. You’ll see each tag firing and every important parameter showing inside GA4, including purchase-specific fields like transaction_id, shipping, and tax—so your revenue attribution is accurate for Google Ads, Meta Ads, and remarketing.