You are moving from WooCommerce to Shopify. Or from Shopify to a custom platform. Or you are keeping the same platform but doing a full site redesign: new theme, new URL structure, new checkout flow. The project feels like a website problem, and Google Ads feels like a separate thing that will keep running in the background.
It will not keep running the same way. A platform migration or major redesign is one of the most reliable ways to break Google Ads performance, and the problems often take weeks to identify because the symptoms look like ordinary variation rather than a direct consequence of the change.
The Tracking Break Is Almost Guaranteed
Every significant site change creates risk of breaking conversion tracking. This is the highest-priority thing to protect through any migration or redesign.
The specific risks:
URL structure changes. If your thank-you page moved from one URL to another during the redesign, any conversion tags configured to fire on the old URL will stop firing. The Google Ads account will see conversions drop to zero. The store will keep receiving orders. This discrepancy is obvious in retrospect but can take days to notice if no one is watching the conversion data closely around the migration date.
Checkout flow changes. Moving to a new checkout system, whether a new platform’s native checkout or an upgraded version of an existing one, changes where and how conversion events fire. A tag that was correctly placed in the old checkout flow may not exist or may fire at the wrong step in the new one.
GTM configuration. Google Tag Manager is the layer that manages most conversion tracking. A site migration often involves moving or re-implementing the GTM container. If the container is implemented differently on the new site (wrong placement, missing from certain page templates, firing before the DOM loads correctly), conversion tracking breaks partially or completely.
New app or plugin conflicts. The new platform or new theme may come with its own marketing integrations. If those integrations add another Google Ads conversion tag, the result is double-counting. Every order triggers two conversion events. ROAS appears to double overnight.
The right approach is to document your current tracking setup in detail before any migration, then verify each piece of the tracking against actual test orders after the migration, before any changes go live to real traffic.
Product Feed Changes and Their Effect on Shopping
If you are migrating platforms, your Shopify or WooCommerce product feed will change. A new product feed means new product IDs (the unique identifiers in the feed), new URL patterns for product pages, and potentially new category structures.
A fresh product feed submitted to Google Merchant Center starts from scratch in Google’s systems. Google needs time to process, validate, and begin serving the new feed. During this period, your Shopping campaigns may have reduced impression share or run with incomplete product coverage.
More importantly, if product IDs in the new feed do not match the product IDs in the existing feed, the historical performance data associated with the old products is not carried over. The new products are treated as new entries, with no click-through rate history or quality signals built up from the old campaign history. This can mean lower Shopping positions for all products temporarily, even if the products themselves are identical.
If possible, preserve product IDs during a platform migration. This is often possible when moving from one Shopify instance to another, or when the new platform allows custom product ID fields. For migrations between very different systems, it may not be feasible, and the performance reset is unavoidable.
URL Changes and Their Effect on Campaign Links
If product page URLs change during a migration (because the URL structure of the new platform differs from the old one), any ad destination URLs pointing to old product pages will break. Users who click Shopping ads will land on 404 error pages.
Shopping campaign product URLs are pulled from the feed, so if the feed is updated to reflect new URLs, this is handled automatically. But Search campaign destination URLs, if you have them pointing to specific pages, need to be updated manually.
URL redirects from old to new URLs help with SEO and direct traffic but do not always solve the click-destination problem in ads, depending on how redirects interact with conversion tracking. A redirect can cause the conversion tag to fire on the old URL before the redirect completes, or skip it on the new URL after the redirect. Testing actual clicks through the redirect path is necessary to confirm the tracking is intact.
Campaign Learning Period Disruption
Even if tracking survives the migration intact, a major site change affects conversion rates in ways that can disrupt the bidding algorithm.
If the new site or redesign converts at a different rate than the old site (better or worse), the algorithm is now operating on historical data that no longer reflects current reality. It may bid aggressively based on a historical conversion rate that the redesign has reduced. Or it may be overly conservative based on a historical conversion rate that the redesigned checkout has actually improved.
This adjustment period can take two to four weeks. It manifests as inconsistent performance: some days good, some days unexpectedly poor, without obvious cause. The algorithm is recalibrating to new conversion rate signals.
During this period, making additional changes to campaign structure, bids, or budgets extends the disruption. Patience while the algorithm adjusts is usually the right call, as long as the tracking is confirmed to be working correctly.
The Timing Problem
Migrations and redesigns often go live at the same time as other business changes: new products, new pricing, a seasonal push, a sale. This creates a situation where multiple variables change simultaneously and it becomes very difficult to attribute performance changes to any single cause.
The recommendation is to time platform migrations or major redesigns during low-traffic, low-stakes periods in the business cycle, not during peak season. And to stabilize Google Ads performance for at least two weeks before launching any other major campaign changes.
If the migration timing is dictated by external factors (a platform contract ending, a developer schedule), then at minimum, document the migration date precisely in both the Google Ads change history and any external notes, so that any performance changes can be mapped to the migration event clearly.
Getting This Fixed
Platform migrations and redesigns are a common source of Google Ads problems that are diagnosed weeks or months after the fact, once the damage to campaign learning history and tracking integrity has already been done.
The right approach involves a pre-migration tracking audit, careful timing, post-migration verification, and monitoring for the weeks following the change. This is exactly the kind of work I do for stores going through significant site changes.
If you are planning a migration or redesign and want to make sure your Google Ads setup survives it intact, reach out at adnanagic.com/#contact.
Part of the Google Ads for Store Owners series, written for ecommerce owners who want their ad spend to actually work.
Related Posts
- Shopify Owners: Why Your Google Ads Conversion Numbers Are Probably Wrong
- Why Your Google Ads Stopped Working After Months of Being Profitable
- The Real Cost of Bad Conversion Tracking
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