Hey Matthias! @teegeschwister @LOVINDOG
You will find multiple threads on this particular topic via the community search bar above. And there are multiple possible reasons for this, such as, for example, you won’t see stats on “added to cart”, “checkout reached”, and “converted session” when the accelerated checkout buttons are used since they bypass the cart.
Also, if you are using a pop out or “fly out” from the top header area the add to cart is not being tracked, so it’s better to use a “cart page” as tracking relies on the page change and pop out carts don’t provide that.
I agree that there can be discrepancies visible within Shopify Analytics, for example, with the missing ‘Add to Cart’ to Order conversion. However, I do not believe that Google is reporting more sessions, but just that Shopify data is not able to track all sessions for different reasons.
To give an order example that indicates this missing conversion, if you add a “City” filter to the Online store conversion over time report and enter a city, some orders may not be visible as a conversion (nor as an ‘Add to Cart’ or ‘Reached Checkout’) while other orders will.
For more context on when a session has been converted, the summary is “sessions in which shoppers added one or more items to their shopping carts, proceeded to the checkout, and then purchased the items”, so the conversion would not show if any of these steps are not fulfilled (as in the first example above).
More detail on that can be found here: Analytics · Shopify Help Center and there has not been any changes to the way that conversions are tracked.
Session tracking is strongly affected by Apple’s ATT and Safari’s ITP as well as by 3rd party Cookie consent managers. Session discrepancies can be related to these apps and cookie tracking in recent months has become much stricter.
Hope that helps!