A new CMS does not by itself worsen rankings. What worsens them is what migrations often drop: old URLs, titles, internal links and signals to the search engine. If these are carried over deliberately, traffic swings are temporary; if not, they become permanent loss.
Why changing the CMS puts rankings at risk
Google ranks URLs, not systems. Each page in search is tied to its address, its content and the links pointing to it. A new CMS often builds a different URL structure (/products/ instead of /lv/produkti/), different titles and a different linking system. To the search engine that is a different site, unless you say it is the same one.
Google’s documentation says even a correctly done move causes temporary ranking fluctuations, and for a medium-sized site the transition can take a few weeks or longer (Google Search Central). So the goal is not “no fluctuation” but “a dip that recovers”.
Step 1: collect all old URLs
Before any development, build a full list of current URLs. Google advises gathering them from several sources: the sitemap, server logs, the CMS and analytics. One source always misses pages. Add URLs with external links pointing at them and the pages with the most clicks in Search Console. These are your risk zone and need the most care.
Step 2: give every URL a place on the new site
Build a table: old URL, new URL, action. The action is one of three:
- move to an equivalent page;
- merge with another page if the content duplicates;
- remove if the page has no value; it then returns 404 or 410, not a redirect to the home page.
Google warns against sending many old URLs to one unrelated page such as the new home page. Each old URL should redirect to its own destination.
Step 3: set permanent redirects
Use server-side permanent redirects (301 or 308), not JavaScript. Google interprets these most reliably, whereas JavaScript redirects may not be seen if rendering fails (Google Search Central: redirects). Two things are often forgotten:
- Chains. Old URL → intermediate URL → new URL. Each old URL should go straight to its destination.
- Duration. Keep redirects for at least a year, longer if possible.
If the new CMS cannot load a redirect list from a file, ask about it when choosing the CMS, not on launch day.
Step 4: carry over what the search engine sees
Add columns to the URL table for content that affects how a page appears in search:
- title and description; Google recommends a unique, descriptive title for each page (Google Search Central: title links);
- H1 and subheadings;
- the canonical URL, pointing to the page itself;
- image alt text;
- internal links, which should point to the new URLs rather than rely on redirects;
- language versions and their annotations on a multilingual site (see hreflang mistakes).
This is where most is lost. A new CMS often generates titles from a template by default (“Page name | Site name”), and all pages start to look the same.
Step 5: test before launch
In a non-public environment, check that each old URL from the table returns 301 and the destination returns 200; that there are no chains; that new pages have titles, descriptions, H1 and canonical; and that internal links do not point to the test domain.
Protect the test environment with a password, not only robots.txt. Google explains that robots.txt manages crawling and is not a way to keep a page out of search (Google Search Central: robots.txt). After launch make sure noindex is removed from the new site. A forgotten noindex is one reason traffic vanishes; there is a separate article on it.
After launch
Switch on the redirects, check the ten most important URLs with the URL inspection tool, submit the new sitemap in Search Console and watch indexing and queries for the first weeks. Old-URL traffic should fall while new-URL traffic grows; if single pages dropped sharply, check exactly those.
Decision rule
- If the new CMS can keep existing URLs, keep them; it is the cheapest safeguard.
- If URLs change, do not launch without a full URL map and 301 redirects.
- If there is no time for the map, postpone the launch rather than hoping rankings recover on their own.
- Between a CMS that does not let you manage URLs, titles and redirects and one that does, choose the second.
As a web development studio we start migrations with the URL map and only then move to design and code. The same work applies when a shop moves platform (online shop development). On whether to rebuild at all, see the old website article. If you plan a move, describe your current situation: discuss your project.
