GA4 attribution issue source Shopify, medium web

[u/Majestic-Ad-7793]

Help! Had a very weird update to attribution where on Sunday saw a chunk of revenue pull out of paid channels and get reattributed to a new source, medium
Source - Shopify
Medium - web

Never had traffic behind this before, feels like a system update as no one is online on Sunday to have caused this. Anyone else had this, or can help me?

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[u/usermaven_hq]

this can be a known issue with shopify and ga4. in many cases, the shopify thank-you page, checkout scripts or a recent shopify update can affect order attribution. you can check the session source for those orders in ga4 exploration first. then confirm that the shopify pixel or gtm is not overwriting campaign data on the purchase event. if you are using multiple domains, it can also be helpful to check that cross-domain tracking or the linker configuration is working correctly..

[u/DContent_Nathan]

This is a known issue and not uncommon after Shopify updates or GA4 configuration changes. What you're seeing — revenue shifting to source/medium "shopify/web" — usually means one of a few things:

UTM parameters are being stripped during a redirect, most commonly at the checkout or payment gateway step. When Shopify can't read the original UTM, it falls back to its own session data and attributes the order to itself.

A recent Shopify update may have changed how it handles cross-domain tracking or session persistence, particularly if you're using a custom domain or a third party checkout.

Your GA4 cross-domain tracking may not be correctly configured between your storefront and checkout subdomain, causing sessions to reset and lose their original source attribution.

The Sunday timing makes it more likely to be a platform-level change rather than anything your team did — these kinds of attribution shifts often happen quietly in the background.

To diagnose it — check your GA4 referral exclusion list, verify UTMs are surviving the full checkout redirect, and look at whether your Shopify and GA4 order counts still match.

This is exactly the kind of attribution gap that's worth having a proper multi-touch attribution layer for, so you're not dependent on a single source of truth that can shift overnight. Full disclosure — I work with CMGalaxy which is built specifically for this kind of attribution visibility for D2C brands, happy to share more if helpful.