Shopify Theme Upgrade — Resolving 3 Years of Tracking Debt

The Challenge

The client’s Shopify store was running a theme version from early 2022. Over three years, their previous agency had layered on extensive customisations — custom product pages, a bespoke mega menu, modified cart drawers, and several third-party app integrations hardcoded into theme files. The theme had never been updated because every attempted upgrade broke the customisations.

The tracking consequences of this were severe. Shopify’s native ecommerce events had changed significantly since 2021, and the client’s theme was still emitting the old event format. Their GA4 ecommerce tracking was effectively broken. The purchase event was firing intermittently because it relied on a deprecated checkout.liquid integration that Shopify had partially removed during platform updates. Their Facebook pixel was missing AddToCart and ViewContent events entirely because the theme’s cart drawer used custom JavaScript that bypassed the standard Shopify event hooks.

The business impact was concrete: Google Ads was receiving 0 actual conversions, which meant their automated bidding was systematically undervaluing the account’s true performance and underspending as a result.

Our Approach

We treated this as a parallel rebuild rather than an in-place upgrade. We created a duplicate theme, upgraded it to the latest version (8.1, as of the project date), and then methodically re-implemented each customisation against the new theme architecture.

The mega menu and custom product pages were rebuilt using Shopify’s updated section and block architecture, which made them maintainable going forward rather than hardcoded overrides. The cart drawer was rebuilt to use Shopify’s standard Section Rendering API, which meant it would emit proper cart events without custom instrumentation.

We also audited and rebuilt all third-party app integrations. Several apps had injected JavaScript directly into the old theme’s layout/theme.liquid that conflicted with the new event model. We moved these into proper Shopify app blocks or GTM tags where possible, and sandboxed the rest using script injection controls.

Along the way, we also discovered a poorly implemented robots.txt rule that was blocking crawling of the product variant pages by Google Bot and other crawlers. This was affecting both organic performance and creating disapprovals in Google Merchant Centre as Google couldn’t verify the page information against the feed.

The Results

Post-migration, tracked transactions & othe key events in GA4 returned to normal level — reflecting the true transaction volume that had been invisible for years. Google Ads conversion tracking went from capturing 0 conversion to a consistent stream of conversions for the campaigns to optimise against.

GMC product listing returned to expected levels from ~20 approved products to ~35,500 approved products and variants. Google search console is also reporting an increase in page indexing and traffic has so far increased 60% to product pages, although we expect these indexing issues to take longer to fully resolve, it has immediately helped aid the recovery of the site and the business.

With accurate conversion data & a useable product feed feeding into Smart Bidding, Google Ads is on the road to recovery, just in time for their busiest period of the year. Initial results are showing a much better optimisation pattern, PMax performance in particularly has rebounded due to having optimisation signals and a working product feed.