Mobile Budget Was About to Be Cut. Mobile Was Starting 62% of All Purchases.

The situation

A US consumer electronics brand was spending $55K/month on Meta and Google. GA4 showed mobile with a 0.8% conversion rate and desktop at 4.2%. The VP of marketing had built a business case to cut mobile spend by 70%. Before executing, they asked me to validate the data.

The problem

The 0.8% mobile conversion rate was technically accurate — in isolation. What it did not show was what happened after the mobile session ended. For electronics buyers with average order values of $280–400, a 2–3 day research cycle was typical: first visit on mobile from an ad, then comparison shopping, then final purchase on desktop days later. GA4's default session-scoped attribution credited the conversion to the session it occurred in. Desktop appeared to convert independently — but it was almost always the final step in a journey that started on mobile.

What we did

1. Implemented GA4 User ID tracking — when a user logs in, their Shopify Customer ID is passed to GA4 as user_id, stitching cross-device sessions into a single journey
2. Built a cross-device path report in GA4 Explorations showing the actual device sequence for every purchase in the prior 90 days
3. Implemented Google Ads Enhanced Conversions with hashed email — allows Google to independently match mobile ad clicks to desktop purchases
4. Configured Meta Advanced Matching with hashed email — links mobile ad impressions to desktop purchases via Meta account login
5. Built a Looker Studio cross-device report updated weekly, showing mobile's true assisted conversion contribution

Why it worked

Single-device conversion rate is one of the most dangerously misleading metrics in digital analytics. Electronics and high-ticket categories always involve multiple devices — and last-touch session attribution always credits desktop while mobile does the discovery work. The mobile budget that was about to be cut ended up being the most valuable spend in the account.