Replatforming an eCommerce site is frightening, above all when the site already lives on organic traffic. If Google indexes thousands of URLs, if many pages have picked up links over the years and if part of the revenue comes from organic search, a badly handled migration can do enormous damage.
In October 2025 we moved a heavily indexed eCommerce site, QuattrozampeShop.it, onto a new custom platform. The priority was not simply "rebuilding the site": it was not losing SEO traffic, not losing revenue and not throwing away the history built up over the years.
The outcome was what a migration should achieve: a small, physiological dip at the start, a gradual settling of the new URLs over the following weeks, then growth. Today the site turns over more than before, has more indexed keywords and benefits from a technical structure designed to create new SEO pages without turning the URL set into chaos.
Why an eCommerce migration is dangerous
Plenty of owners think that changing site only means moving design, products and orders. In reality, as far as Google is concerned, a platform change can mean losing crucial reference points:
- product URLs that have been indexed for years;
- categories that receive organic traffic;
- old PHP pages still present in the results;
- product images ranking in Google Images;
- external links accumulated over time;
- reviews and useful content that, if handled badly, become invisible to crawlers.
The problem is that the damage is often noticed too late: Search Console starts showing 404s, traffic falls, sales slow down and the agency tries to "fix it afterwards". In a serious SEO migration, afterwards is too late to recover everything.
The tricky part: the old URLs were not simple
On the old site, product and category URLs had a very similar structure. A product page URL and a category URL could both look like ordinary HTML pages. On top of that, some pages that looked like brand pages were actually categories with a filter already applied.
That pointed to a legacy routing system: the platform received the URL, then decided internally whether to show a product, a category, a brand page or a filtered category.
The new custom eCommerce, by contrast, uses a different and cleaner logic: catalogue pages and facets can become genuinely indexable pages, with short, readable URLs and no messy query string parameters.
Examples of the URL logic:
/cats/for a category;/oasyfor a brand;/cats_oasy/for category plus brand;/cats--grain-free.htmlfor a category with an indexable filter;/cats_oasy--grain-free.htmfor brand, category and filter.
This structure is far more useful for SEO than URLs with ?, parameters and filters that are hard to index. But precisely because the logic changes, you cannot migrate by eye: you need surgical mapping.
The solution: a 301 map built before the switch
Before launch we crawled the important URLs on the old site and mapped them to their new destinations. The work covered catalogue pages, brand pages, filtered pages and generic content.
To avoid slowing down a site with a lot of traffic, the mapping was stored in a dedicated dictionary, so the database was not queried needlessly on every request. Product URLs were kept unchanged wherever possible, to preserve the most sensitive part of the existing SEO.
When the system could no longer find an old resource in its original position, the migration page stepped in: it looked the match up in the dictionary and returned a 301 redirect to the correct new URL.
We also recovered the old indexed PHP URLs
Another hidden risk was the old dynamic URLs, still indexed or linked from other sites. Pages such as visarticolo.php, main.php, shop.php?marchio= and shop.php?cat= existed in the site's history and could still bring in traffic or SEO signals.
Redirecting the tidy URLs was not enough. We also intercepted the old calls with query strings, read the useful parameters and sent users to the correct new page with a 301. For some very old resources we had to look the matches up manually and reconstruct category IDs and brand IDs.
This is one of the steps that often gets skipped: an old eCommerce site does not only have the URLs you can see in the menu. It has years of legacy URLs, external links, old campaigns, images, forgotten pages and paths that are still present in Google.
We protected the product images too
For many eCommerce sites, Google Images is a real source of traffic and sales. On the old QuattrozampeShop, product images were served in several different ways: files in the root, images on a subdomain, thumbnails generated by thumb.php and legacy paths.
To avoid losing that visibility we replicated the structure of the important images, kept the historic paths alive and handled redirects where they were needed. That way the new site stayed clean internally, while the images Google already knew about did not start returning errors.
Reviews, content and AI: not just a technical migration
Once the SEO foundations were protected, the new custom eCommerce made a step forward possible.
Filtered pages are no longer treated as mere technical combinations: they can become new SEO pages, with readable URLs and dedicated copy. The first draft of that copy can be produced with AI support, then reviewed and improved over time, page by page.
Product pages also include an AI-generated section that summarises the information on the page, customer questions and answers, and reviews. The aim is not to fill the page with generic text, but to help the user resolve concrete doubts before buying.
On top of that there is a dedicated AI chatbot, designed to answer common catalogue questions on the spot, and brand pages with custom design work, which are far stronger than identikit brand listings.
Performance: a Lighthouse test at 99/100
The migration was not only about SEO. In a Lighthouse lab measurement, on a specific page and under specific test conditions, the new site reached 99/100. That is a single data point, not a guarantee that holds for every page, device or visit; to judge the real experience it has to sit alongside field data and monitoring of the main user journeys.
On an eCommerce site, speed is not a cosmetic detail. A faster catalogue helps Google crawl more effectively and helps users complete a purchase with less friction.
What happened after launch
After the switch, the SEO signals followed the pattern we expected: an initial micro-dip, then a progressive settling onto the new URLs. No sudden collapse, no weeks of panic, no improvised recovery once the damage was done.
Within a few weeks the curve stabilised and then started to climb. The site began to turn over more than before and to widen the number of indexed keywords, helped by the new architecture of categories, brands and SEO-ready facets.
What to ask your agency before you replatform
If you are thinking of changing eCommerce platform, rebuilding the site or moving from a standard CMS to a custom solution, these are the questions to ask before signing:
To prepare the release you can also use the technical eCommerce SEO migration checklist, check how canonicals for products and facets are handled, and compare the platform's constraints with the page on custom eCommerce development.
- Have you run a full crawl of the current URLs? Not just the menu and the products, but old indexed URLs, PHP pages, query strings, images and legacy content.
- Is there an old URL → new URL 301 map? It has to be prepared before go-live, not afterwards.
- Will the product URLs change? If they change, you need to know why and how they will be redirected.
- How will you handle the indexed images? If they disappear, you could lose traffic from Google Images.
- Have you checked the old pages with parameters? URLs such as
shop.php?cat=orvisarticolo.php?id=are often still alive as far as Google is concerned. - How will you monitor 404s, 301s and 200s after launch? You need a crawler and you need to check the actual responses, not just look at the homepage.
- Does the new platform allow clean, indexable facets? New SEO pages need short URLs, dedicated copy and a sensible structure.
- Who reviews the AI copy? AI speeds things up, but SEO quality grows when the text is checked and improved over time.
- What is your plan for Search Console? Sitemaps, coverage, indexing and redirects have to be monitored in the days and weeks that follow.
- What happens if something does not add up? There has to be a technical fallback plan ready in advance.
Frequently asked questions
Will I lose Google traffic if I change eCommerce platform?
Not necessarily. A small dip can be normal, but a collapse is not. The difference comes from crawling in advance, 301 mapping, image handling, post go-live testing and a coherent URL structure.
When should the 301 redirect map be prepared?
Before launch. Preparing it afterwards means leaving Google and users in front of errors, missing pages or generic redirects. Once the damage has already shown up in Search Console and in sales, recovering everything can be impossible.
Are filtered URLs a problem for SEO?
It depends how they are built. If they are long URLs with uncontrolled parameters and combinations, they can create confusion. If instead they become real pages, with short URLs, SEO copy and clear logic, they can increase the number of indexed keywords.
Is it worth keeping the old product URLs?
Where possible, yes. Product pages often concentrate traffic, links, images and history. If they have to change, you need a precise 301 redirect to the matching new page.
Why check the images during a migration as well?
Because a lot of sales start in Google Images, especially in sectors with very visual catalogues. If the old indexed images start returning errors, you lose a source of traffic that is often underestimated.
Can AI help the SEO of an eCommerce site?
Yes, if it is used as an accelerator and not as a substitute for strategy. It can generate first drafts of category copy, product summaries and useful answers, but human review is needed to avoid generic or duplicate content.
What should I ask my agency before the switch?
Ask about the URL crawl, the 301 redirect map, image handling, the Search Console plan, checks on old PHP or query string URLs, crawler testing and monitoring of response codes after go-live.
Can a badly executed migration be recovered?
Sometimes part of it can be recovered, but you should not count on it. If Google finds errors for weeks, if links land on 404s and if the old URLs disappear without redirects, part of the history can be lost for good. Real protection happens beforehand.
Thinking of changing eCommerce platform but afraid of losing organic traffic? Before you publish the new site, let's audit the current structure, the indexed URLs, the redirects you need and the SEO opportunities in the new platform.