Moving a website to a new platform looks like a purely technical job: transfer the products, change the design, launch. But a migration is exactly where businesses lose what they built over years - their search rankings. And search is free traffic, meaning buyers you no longer pay for with ads. Below: where SEO gets lost during a migration, what it costs in money, and how to get through a migration without a collapse.
Why a migration is a risk zone for SEO
A search engine remembers your pages by their addresses, and it does so for years. Every product page, category, and article lives at a specific URL, and that URL is what appears in search results and brings traffic.
During a migration, addresses often change: there was one structure, now there is another. If an old address simply stops opening, this is what happens: a person clicks a familiar link in search and lands on an empty 404 page. The search engine sees that the page is dead and, over time, drops it from the results. The traffic that came to that page for years goes to zero.
The most treacherous part is that it does not drop immediately. For the first weeks after the migration everything looks fine, then rankings start to slide, and the cause is not noticed right away. By then the traffic has already fallen.
What a mistake costs
In money terms, the cost of a migration mistake is simple to count: however many buyers used to come from search for free, that is how many you lose until rankings return.
Say a noticeable share of your orders came from search with no ad spend. After a failed migration that flow drops. To avoid losing revenue, you turn to paid advertising - and start paying for the buyers who used to arrive for free. And recovering rankings after a failure is not a matter of a week but of months. All that time you either lose revenue or pay extra for ads. The cost of the mistake is not a one-off; it is spread over months.
The paradox is that doing the migration properly costs far less than recovering afterwards. It is the kind of saving at the start that backfires.
What it looks like in practice: our own migration
Let us show it on our own store, IWANT, which we moved from a third-party platform to our own engine built on Next.js. It had years of history behind it - thousands of pages in the index - so we treated SEO as a separate task. The technical part was fully done, yet search traffic still did not come back right away - and that is the most useful part of the story.
1. Every page moved with a 301 redirect
Every page moved to its new address with a 301 redirect. A 301 means "moved permanently, here": both the person and the search engine are sent automatically from the old address to the new one, and the page's weight in search results is carried over. No 404 pages where traffic used to be.
2. Redirects built from analytics, not by eye
Not all pages are equally valuable. We pulled up the real analytics - which URLs actually brought traffic - and covered those with redirects first. The redirect map was built from data, not intuition. Priority went to the pages that were actually working.
3. The sitemap comes from the database
The sitemap (a file listing all pages for the search engine) is generated straight from the database rather than maintained by hand. Every live page enters the sitemap automatically as soon as it appears in the database.
4. What was missing: pages with no path to them
The redirects were working - a sample of 120 old product addresses led to live product pages in a single hop. And yet eight weeks after the switch, search traffic had not returned. The cause turned out to be two settings of the new site: we did not include sold-out products in the sitemap ("why show something that cannot be bought") and we hid them from the catalog listings ("the page is available at its direct address anyway").
Together this produced 2,041 live pages with no sitemap entry and not a single internal link. Formally the pages work and return 200; in practice the search engine cannot find them, because it follows links and the sitemap. A subtlety specific to modern frameworks: links that are loaded by a script in the browser do not count for this purpose - the links need to be in the source HTML.
The main conclusion we carried into every later migration: a 301 redirect transfers a page's weight, but it does not keep the page in the index. A page lives as long as there is a path to it - a sitemap entry and at least one server-rendered internal link. After we reworked the product pages, the sitemap grew to 3,786 pages instead of 1,740, and the pages we had deliberately not carried over started returning 410 instead of leaving their status undefined. For more on the platform and the stack itself, see our breakdown when to move from a platform to Next.js.
An honest note on the result: the fixes went live at the end of July, and it is too early to talk about traffic recovery - search engines recrawl a site of this size over weeks. We will share growth figures when they exist, not before. What this story is worth is the cause itself, and it is worth checking on your own site before it costs you months.
A migration checklist for keeping your traffic
- collect every old address that brought traffic (from your search analytics, for example Google Search Console);
- set up a 301 redirect from each of them to the new address;
- check that there are no 404 errors on pages that had traffic;
- update the sitemap and submit the current one to the search engine;
- check that every live page is in the sitemap - or deliberately closed from indexing; there should be no third state;
- make sure at least one link in the source HTML leads to every live page, not only a script-loaded one;
- return a 410 code for anything removed for good, not a placeholder page and not a redirect to the home page;
- watch rankings and indexing for six to eight weeks, not just the first week: a drop is not visible right away.
Who does not need to worry
If the site is young and gets almost no traffic from search, there is essentially nothing to lose. You can migrate more calmly: keep an eye on it, but the cost of a mistake is small.
If search is a noticeable sales channel for you, migrating without an SEO plan is a game with real money. Here redirects and the sitemap are a required part of the migration, built into the work from the start.
Planning a migration and worried about your search traffic? We will review your structure and show what to cover with redirects first.
