Earlier this year I migrated MatthewMamet.com from one platform to another. The site had accumulated several years of content, some organic rankings, and a URL structure that did not map cleanly to the destination platform's default permalink format. If I had just launched the new site without handling the redirect layer, I would have handed Google a 404 page for every indexed URL and wiped out whatever ranking equity existed.
I did not do that. But I have watched companies do the equivalent during platform migrations and redesigns, and the recovery is painful. Rankings that took two years to build can disappear in a crawl cycle. Traffic does not come back automatically when you put the new site up.
What actually breaks during a redesign
The SEO risk in a website redesign is not the new design. Google does not care what your site looks like. The risk is URL changes. When a page that Google has indexed at one address suddenly returns a 404 because the URL structure changed, Google drops it from the index. The page rating, the backlinks pointing to it, the click-through history - all of that accumulated value is now attached to an address that no longer exists.
The other risk is content changes that strip the signals Google was using to rank the page. If a page that was ranking for a specific keyword gets redesigned and the content moves to a different page, or the heading structure changes, or the page gets split or merged, the ranking signal weakens even if the URL stays the same.
The redirect layer
The 301 redirect is the standard tool. It tells search engines and browsers that a URL has permanently moved to a new address, and to transfer the ranking equity to the new URL. For a platform migration, this means building a complete map of old URLs to new URLs before you launch, and deploying it the moment the new site goes live.
On the migration, I used Cloudflare's redirect rules to handle the URL mapping. The old platform had a different permalink structure. Every old URL needed a corresponding rule that pointed to the correct new address. This sounds tedious because it is. But it is the work that keeps a multi-year investment in content from evaporating in a week.
At Embarc, we learned this from clients
Pharma and biotech clients were serious about their web presence. A Lunesta redesign or an Athena Health site migration had compliance requirements on top of the standard SEO considerations. We built a redirect audit and deployment process into every project because we had seen what happened when it was skipped. One client lost a significant portion of organic traffic after a previous agency launched a redesign without handling URL changes. It took eight months to recover.
The SEO frameworks we built at Embarc for pharma clients were not sophisticated by modern standards, but the core principle was the same: do not lose what you have while you are building what comes next. That constraint applies whether you are running a regulated pharma web presence or a personal consulting site.
The checklist that matters
Before any site migration or major redesign: crawl your current site and export every indexed URL. Map every URL that is changing to its new address. Deploy 301 redirects before or at launch, not after. Submit the new sitemap to Google Search Console immediately. Use IndexNow to push the updated URLs to search engines rather than waiting for them to recrawl organically. Then monitor Search Console for 404 errors in the weeks after launch and fix any gaps in your redirect map.
