Changing eCommerce platform is one of the most delicate operations a company can undertake. Not because it is impossible, but because much of the damage is invisible on launch day. It shows up later: organic traffic falling, historic URLs returning 404, images disappearing from Google, products that can no longer be found, Ads campaigns landing on the wrong pages and revenue starting to slide.
The point is simple: an eCommerce site is not just design, products and checkout. It is also years of indexed URLs, external links, category pages, facets, brands, images, reviews, structured data, sitemaps, feeds, campaigns and signals Google has learned over time.
When you change site, Google has to understand that those pages are not dead: they have moved. If you don't explain that properly before go-live, you can run around afterwards, but part of the damage may already have passed through Search Console and through your sales.
The real risk isn't the new site: it's the changeover
Many owners approach a rebuild with an entirely reasonable fear: "if I change eCommerce platform, will I lose all my Google traffic?". The correct answer is: not necessarily. A small dip while things settle can be normal. A collapse, on the other hand, usually means something was handled badly.
In the case study on the QuattrozampeShop SEO migration we described a real changeover: an initial micro-dip, a gradual settling of the new URLs, then growth. That is the goal: not pretending Google has nothing to recalculate, but preparing everything so the move is understandable, measurable and reversible where it needs to be.
The problem is that many migrations are treated like a theme change: publish the new site, then see if anything is broken. On an eCommerce site with organic traffic, that is a terrible idea.
The technical basics are not a matter of opinion
Google Search Central states clearly that when a site changes URLs you have to plan the migration, set up correct redirects, update sitemaps, monitor traffic and check for errors after launch. The official documentation on site moves with URL changes and on 301 redirects leaves little room for improvisation.
In practice: if you change URLs, you have to tell search engines where the old pages have gone. Not with generic redirects pointing everything at the homepage, not with "we'll sort it out later", not with a plugin installed at the last minute. You need a precise map.
The SEO checklist before changing eCommerce site
This is the list an owner should insist on before the new site is published. It is not theory: these are the checks that stop you losing traffic, data, history and sales.
1. Crawl every URL on the old site
Before changing platform you need to know which URLs actually exist. Exporting the menu or eyeballing the most important pages is not enough. You need a crawl of the site plus a cross-check against Search Console, Analytics, sitemaps, the Merchant Center feed, old campaigns and backlinks.
What to collect:
- main categories;
- secondary categories;
- product pages;
- brand pages;
- indexed facet pages;
- CMS pages and guides;
- parameter URLs that still get visits;
- old legacy URLs still present in Google;
- indexed product images;
- landing pages used by Google Ads, Meta Ads or newsletters.
If a URL receives traffic, links or impressions, it should not be ignored just because it no longer appears in the menu.
2. Build a 301 redirect map, old URL → new URL
The redirect map is the heart of the migration. Every important old URL has to have a coherent new destination.
An old category has to go to the equivalent new category. An old product page has to go to the same product, not to a generic category. A brand has to go to the new brand page. A facet page with SEO value has to go to the corresponding new facet page, where one exists.
The most common mistakes are:
- redirecting too many pages to the homepage;
- leaving old products on 404 for no reason;
- creating redirect chains;
- using temporary redirects when the change is permanent;
- ignoring parameter URLs that are still indexed;
- forgetting images, PDFs, blog pages and Ads landing pages.
A 301 redirect is not a technical formality. It is how you transfer users, crawlers and signals from the old architecture to the new one.
3. Decide which URLs to keep identical
Changing URLs is not always necessary. If a product page already ranks well and its URL is clean, it is often best to keep it exactly as it is. Every URL change is a small risk; if it brings no real benefit, avoid it.
The new platform has to be better, not just different. When we work on a custom eCommerce build, we assess which URLs to keep, which to clean up and which to turn into stronger new pages.
4. Check categories, brands and facets
Categories are often the most important part of eCommerce SEO. But in real catalogues traffic can also come from brand pages and filtered pages.
If the old site had facet URLs that were already indexed, you need to work out which of them deserve a genuine new page and which should be blocked, merged or redirected.
We have already set out our approach to this in the article on automatic eCommerce facets with AI and real SEO pages: the point is not to index everything, but to create useful commercial pages, with readable URLs, dedicated copy and relevant products.
5. Prepare canonicals, noindex and pagination
A migration can create unintentional duplicates: products reachable from several categories, parameter URLs, near-identical facets, product variants, pages sorted in different ways.
Before launch you have to decide:
- which pages are canonical;
- which facet combinations must not be indexed;
- how to handle colour, size or format variants;
- how to avoid empty or near-empty pages;
- how to treat out-of-stock or discontinued products.
If these rules are improvised after publication, Search Console will start showing problems that could have been prevented.
6. Update the XML sitemap and robots.txt
The new site's sitemap should contain only URLs that are publishable, canonical and useful. It should not be a bin holding every possible combination in the catalogue.
After go-live you have to submit the new sitemap in Search Console and check that Google reads it correctly. The robots.txt file needs verifying too: staging environments, temporary blocks and old rules end up live more often than you would think.
7. Protect images and files that are already indexed
Many eCommerce sites underestimate Google Images. In several sectors, product images bring traffic, comparisons and sales. If you change image paths without redirects, or without keeping the old files available, you can lose a slice of visibility nobody was monitoring.
So before the change you need to know where the images are, which paths are indexed and whether the new system serves them from different URLs.
8. Check product structured data
Product pages have to expose consistent structured data: name, image, price, availability, reviews where present, brand and other useful information. You don't need markup scattered at random; you need data consistent with what the user sees on the page.
This matters especially if the old site already had rich results, or if the catalogue depends heavily on the organic visibility of its products.
9. Don't forget tracking, feeds and campaigns
SEO and marketing don't live apart. When an eCommerce site changes, you also have to check:
- GA4 and eCommerce tracking;
- Google Ads events;
- the purchase conversion;
- the Google Merchant Center feed;
- the final URLs on campaigns;
- landing pages used by PMax, Shopping, Search and remarketing;
- the Meta pixel or server-side tracking;
- the cookie banner and Consent Mode.
A site can be migrated well on the SEO side and still break tracking. And if tracking breaks, campaigns learn the wrong things. We covered this in the article on Google Ads for eCommerce and automation: the data you send the advertising platforms directly influences the algorithm's decisions.
10. Run a pre go-live crawl of the new site
Before publishing you have to crawl the new site in the test environment. Looking at the homepage and placing a couple of test orders is not enough.
You have to check 200, 301 and 404 codes, canonicals, H1s, titles, meta descriptions, noindex, images, internal links, product pages, categories, facets, checkout, basket, information pages and blog content.
The new site has to be checked before it becomes the real site.
11. Prepare a post go-live monitoring plan
Publication day is not the end of the migration: it is the start of the monitoring phase.
In the first hours and the first days you need to watch:
- server logs;
- 404 errors;
- 301 redirects;
- redirect chains;
- excluded pages in Search Console;
- impressions and clicks on the main queries;
- how the most important categories are performing;
- orders and conversions;
- the Merchant Center feed;
- Ads campaigns with updated URLs.
If something doesn't add up, you need to spot it immediately. Waiting a month means leaving Google and your customers in front of errors that could have been fixed in a few hours.
What to ask your agency before it's too late
If you are changing site, these questions belong before go-live. Not after.
- Have you exported every indexed and visited URL? I want to see files, not a verbal reassurance.
- Is there a complete 301 redirect map? Old URL, new URL, status and priority.
- Which URLs will stay identical? And which will change, for a precise reason?
- How are you handling images that are already indexed? Old paths, new paths, redirects and missing files.
- Have you checked old parameter URLs? They are often still in Google or in backlinks.
- Does the new sitemap contain only canonical pages? Or are there pointless facets and duplicates inside it?
- Who is watching Search Console in the days afterwards? You need a named person, not "we'll see".
- Did you crawl the new site before publishing? I want to know how many 404s, noindex tags and canonicals there are before launch.
- Are the Ads campaigns and the Merchant Center feed updated? Paid traffic must not land on dead URLs.
- What is the plan if something goes wrong? Rollback, fast fixes and priorities have to be clear already.
The warning sign: "we'll do the redirects afterwards"
If you hear that sentence, stop. Redirects are prepared beforehand. Afterwards you can refine them, correct them and add the cases that slipped through, but the main structure has to be ready before publication.
A migration with no 301 map is like moving a shop without telling customers the new address. Some will find you anyway, but plenty will get lost on the way.
How we approach an eCommerce migration
At BitHub we start from the real structure of the site, not from the new template. First we work out what is already bringing traffic, which URLs have value, which categories need protecting, which facets can become SEO pages and which parts of the catalogue deserve a better structure.
Then we build the new platform with clean URLs, performance, tracking and room to grow the catalogue without creating chaos. That is the advantage of a custom eCommerce build: you are not forced to accept the logic of a plugin or a CMS, you can design the structure around SEO, data and sales.
The SEO side does not live alone: it connects to Google Ads, Merchant Center, tracking and digital strategy. Because a new site has to rank, but it also has to sell and feed correct data to the campaigns.
Frequently asked questions
How much traffic do you lose when you change eCommerce site?
There is no fixed percentage. A small temporary dip can be normal, especially if many URLs change. A steep, lasting collapse, on the other hand, usually points to problems with redirects, indexing, content, canonicals or tracking.
Do 301 redirects transfer all the SEO value?
301 redirects are the right tool for signalling a permanent move, but they have to be consistent. Redirecting everything to the homepage or creating pointless chains can reduce the quality of the transfer and worsen the user experience.
When should the redirect map be prepared?
Before go-live. After launch you can fix the cases that slipped through, but the main map has to be ready and tested before the new site goes online.
Should I keep the old product URLs?
When they are clean and working well, it is often best to keep them. If they do change, every important old product page needs a precise redirect to the corresponding new one.
Is a sitemap enough for Google to understand the new site?
No. The sitemap helps Google discover the new URLs, but it does not replace redirects, canonicals, internal links and error monitoring. It belongs inside a complete migration, not on its own.
Do images need migrating carefully?
Yes. Product images can receive traffic from Google Images and can be linked from external pages. If they change path or disappear, part of that visibility can be lost.
Can a badly executed SEO migration be recovered?
Sometimes part of it can be recovered, but not always all of it. The more time passes with 404s, wrong redirects and important pages that cannot be indexed, the harder it becomes to get back to where you were.
How long should you monitor Search Console after go-live?
At least for the first few weeks, with frequent checks in the first days. Crawl errors, excluded pages, query drops and problems with sitemaps or canonicals need spotting straight away.
About to change eCommerce platform? Before you publish the new site, we can check URLs, redirects, sitemap, categories, facets, tracking and SEO risks. Preventing a loss of traffic is far better than trying to recover it once revenue has already started to fall.