Site migrations are one of those things that seem like a purely technical project right up until the moment your Google Ads campaigns stop working, your Shopping feed throws a cascade of errors, and your client is texting you on a Saturday morning asking why their revenue fell off a cliff overnight. I've been close enough to that scenario to have strong feelings about it, and what I've learned is that the PPC team needs to be in the room before the migration happens... NOT after.

If your development team or agency is planning to move from one ecommerce platform to another (something to Shopify is probably the most common version of this conversation right now), here is what I'd want every Google Ads practitioner to be checking, in roughly the order I'd be checking it:

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Before Anything Happens

Pick your migration window deliberately.

Pull up Google Analytics and find your lowest-traffic four-hour window AT THE BEGINNING OF A WEEK AND WORKDAY, which for most ecommerce accounts is somewhere in the early morning hours on a Monday or Tuesday. That's your migration window. It sounds almost too simple to mention, but I've seen too many migrations end up "finally happening" on a Friday afternoon because that's when the developer was finally ready to go live, and the resulting chaos was entirely preventable. Protect your highest-traffic windows like they're sacred, because for your client's business, they kind of are. And for the love of all that is good, don't push it live on a Friday unless you all plan to be working over the weekend.

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Audit every URL that matters.

Your product page URLs and core site URLs need to be mapped before migration. If your URL structure is changing (and it often does when you switch platforms), every URL that changes needs a proper 301 redirect in place. This matters for SEO obviously, but it also matters for any Google Ads destination URLs you've hardcoded into campaigns, ad groups, or individual ads. Sitelink extensions, callout extensions, price extensions, anything pointing to a specific page needs to be audited and updated. Missing even a handful of these can trigger ad disapprovals or send paid traffic to error pages, neither of which is a conversation you want to have. Oh, and that being said... you must must must  engage SEO assistance on this migration in whatever form you believe in!

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Check your Shopping feed setup carefully.

If you're using a third-party feed management platform like Feedonomics, DataFeedWatch, or GoDataFeed, the good news is that your feed structure itself is probably going to survive the migration intact, since the provider sits between your platform and Google Merchant Center. The thing you need to verify is how the data gets from your new platform to that provider in the first place. The connection method, the API credentials, the sync frequency, all of that needs to be confirmed before you flip the switch, because a feed that was happily syncing from BigCommerce every hour may need to be completely reconfigured to sync from Shopify. That being said, check the next point below to confirm IDs won't change (again, broken record here, BEFORE you push the button), especially since default IDs on non-Shopify and Shopify sites tend to differ.

For anyone managing feeds directly without a third-party platform, this is significantly more fraught and deserves its own dedicated pre-migration audit. Our writing on Google Merchant Center covers feed setup and troubleshooting in considerable depth if you want to go deeper on this.

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Keep your product IDs consistent. Seriously.

This one cannot be overstated. If your product IDs change during migration (which happens often because of how different platforms generate variant IDs), you are looking at a cascade of problems across your Shopping feed, your dynamic remarketing audiences, your Merchant Center diagnostics, and potentially your campaign structure if you're using product ID-based targeting. Product IDs are the thread that holds the whole system together, and changing them mid-migration without a plan for handling the transition is one of the more reliable ways to create a very bad week for yourself. Product IDs are, according to Google, responsible for maintaining a history of sorts on their backend that impacts your auction and targeting, so don't change those unless you want to... and ensure they aren't changing before you make the feed transition. There are ways to force some platforms to your old IDs, and this should be something you have planned beforehand. IF you absolutely must change your IDs, work through a specific plan to closely monitor and account for any performance changes with campaign and targeting adjustments.

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Verify your conversion tracking setup on the new platform.

Do this before, not after. Understand exactly how conversion events are currently firing, where the tags live (directly on the platform, through Google Tag Manager, or both), and what the new platform's tagging approach will look like. Shopify, for instance, handles checkout page access differently than many other platforms, and conversion tags that fired reliably on BigCommerce checkout pages may need to be reconfigured entirely. If you're using Google Tag Manager, verify that your GTM container will fire correctly on the new platform and that all triggers are set up to match the new site structure.

The good news is, that this is often a great time to actually "reset" your tags (conversion and remarketing) to a more simplified setup, so take this opportunity to do so (that can even help things like pagespeed)!
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Check your remarketing and dynamic remarketing tags.

Your remarketing audiences are built on user behavior tied to your old URL structure and your old platform's product ID format. After migration, verify that the Google Tag is firing on all key pages of the new site, that product ID parameters in dynamic remarketing tags are still matching the format in your Merchant Center feed, and that your audience lists are still populating correctly. A migration that breaks dynamic remarketing quietly, without any obvious error messages, is one of the harder post-migration problems to diagnose. Our writing on remarketing strategy gets into the diagnostic side of this in more depth. Dynamic remarketing tags are absolutely crucial to PMax success in many accounts, and you don't get an obvious warning that something has broken if the system is no longer accurately matching up products visited to products views for a customer... the system will just pick random products to show in the Dynamic Product Ads... so do the work to ensure this is solid already.

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During Migration

Decide ahead of time whether to pause campaigns or leave them running.

There's no universally right answer here: Pausing everything during migration protects you from sending paid traffic to error pages or broken checkout flows, which is a real risk if something in the migration doesn't go as planned. Leaving campaigns running avoids triggering smart bidding relearning periods for campaigns that were performing well. My general lean is to leave all campaigns running if the site will remain accessible throughout and IF you have a relatively high confidence that you've followed all these steps. But that's a judgment call that depends on the migration complexity, the platform, and how confident you are in the timeline. This is also why we recommend doing this at the beginning of a week and day... you actually have the ability to monitor and respond quickly if issues happen!

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Monitor Google Merchant Center closely.

Platform migrations sometimes trigger Google's automated systems to flag changes in your website that prompt re-verification of your Merchant Center account or re-review of your product listings. Keep an eye on the Merchant Center diagnostics throughout the migration window, and don't be surprised if you see a temporary uptick in disapprovals while Google recrawls your updated product pages. Most of these resolve on their own within a few days, but some require manual intervention and it's better to catch them early.

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After Migration

Verify conversion actions before you declare victory.

Put this at the top of the post-migration checklist, above everything else. Go through every conversion action in Google Ads and confirm it's still firing correctly on the new platform. Purchase confirmations, lead form submissions, phone call tracking, newsletter signups, all of it. A migration that breaks conversion tracking silently (meaning campaigns keep running but stop recording conversions) is going to ruin your day (and the bidding algos).

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Think carefully about smart bidding and learning periods.

If your campaigns were in a stable smart bidding phase before migration and you paused them during the switch, restarting them can trigger some degree of relearning (not always). How much relearning depends on how long they were paused and how much historical conversion data they have to draw on. For campaigns with strong conversion history, the relearning period is usually short and relatively painless. For newer campaigns with thinner data, it can take longer. This is also why my main suggestion is to leave things running.

Regardless, set expectations with your client accordingly, and resist the pressure to make major bid strategy changes during the first week post-migration while the algorithm is finding its footing. Our writing on campaign strategy and Google Ads bidding covers the smart bidding relearning question in more depth if you want more context.

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Check site speed on the new platform.

This one sometimes gets forgotten in the migration checklist because it feels more like a development concern than a PPC concern, but site speed affects Quality Score, and Quality Score affects your CPCs and ad rank.. and frankly, customer conversion rates! If your new platform is significantly faster or slower than your old one, you'll want to know that quickly and flag it to the right people, because a speed regression on a Shopify store that was migrated from a highly optimized BigCommerce setup can quietly hurt your paid performance in ways that take a while to connect back to the migration.

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The summary of all of this is that site migrations are one of the highest-risk planned moments for a Google Ads account, and the PPC team being involved early (I'd say at least a month before the planned migration date) is what separates the migrations that go smoothly from the ones that become post-mortems. The checklist above isn't exhaustive and every migration has its own wrinkles, but if you're working through all of these things before, during, and after the switch, you're in a significantly better position than most.

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