Site migrations are one of those things every developer and SEO has to survive at least once. A rebrand, a move from WordPress to Next.js, a new domain, a URL structure cleanup. Whatever the reason, the pattern is always the same: you launch, traffic dips, and then everyone asks the same panicked question. How long until Google catches up?
This month, Google's John Mueller gave an honest answer. As reported in the October 16, 2026 PageTraffic weekly SEO roundup, he explained that website migrations can take longer than four months when Google runs into problems processing redirects, crawling URLs, or understanding changes across a large website. Migration timelines, he said, depend on site size, URL changes, and technical implementation.
That is the honest version. There is no magic "reindex everything" button. But four months is the problem scenario, not the guaranteed one. The difference between a two-week migration and a four-month migration usually comes down to how much you prepared before launch. Here is the checklist I would run.
Before you touch anything: the pre-migration audit
Crawl the old site and export everything. Use a crawler and save every URL, its status code, title, meta description, headings, and word count. This is your ground truth. If you lose traffic later, this file tells you exactly what changed.
Map every URL, one by one. The single biggest cause of long migrations is bad redirect mapping. Every old URL that had traffic, backlinks, or rankings needs a 1:1 301 redirect to its closest new equivalent. Not to the homepage. Not to a category page. To the real equivalent page.
Keep URL slugs clean. Google's Gary Illyes clarified this week (same roundup) that keywords in URLs have minimal impact on rankings, so there is no need to stuff them. Use hyphens instead of underscores to separate words, and if you are rebuilding URLs during the migration, now is the time to clean up the ugly ones. Just remember: every changed URL is another redirect Google has to process, so change only what is worth changing.
Document the old site's Search Console data. Export your top queries, top pages, and backlink profile. Post-launch, you will compare weekly. Without a baseline, you cannot tell "normal settling" apart from "something broke."
The technical setup that actually matters
301s, not 302s, and test them before launch. Set up redirects in a staging environment first and crawl the full old URL list against it. Look for chains (A to B to C), loops, and redirects to 404s. Every chain you leave in place is extra crawl budget burned and extra delay added.
One version of everything. Canonical tags, HTTPS, www vs non-www, trailing slashes. Pick one version and redirect the rest. During a migration is exactly when mixed signals confuse Google the most.
Update internal links to point at the new URLs. Redirects catch external links and bookmarks, but your own internal links should point directly at the new destinations. Crawlers follow internal links first, so make their job easy.
Keep the robots.txt and sitemaps honest. Do not accidentally block staging, and do not forget to unblock it. Submit the new XML sitemap in Search Console on launch day, and keep the old sitemap submitted for a while too, so Google can discover the redirects.
Launch week: watch like a hawk
Monitor indexing daily for the first two weeks. Check the Index Coverage report. A wave of excluded pages or redirect errors in week one is normal noise, but redirect errors that persist into week three are not.
Watch server logs for Googlebot behavior. If Googlebot is still hammering the old URLs weeks later, your redirects are not clean enough. If it is crawling the new URLs steadily, the processing is underway and patience is the right strategy.
Do not redesign everything at once. Mueller's point about Google "understanding changes across a large website" is important. If you change the domain, the URL structure, the design, and the content all in one go, you have given Google a puzzle instead of a map. Stagger big changes when you can.
The 4-month reality check
Here is the honest math. Small site, clean 1:1 redirects, no structural chaos: Google usually processes it in a few weeks. Large site with messy redirects, changed URL patterns, and crawling issues: this is where the 4+ month timeline Mueller described comes from. Your job before launch is to remove every item from the second list.
And one thing to internalize: a traffic dip after a migration is not automatically a penalty. Rankings need the new signals to be reprocessed, re-crawled, and re-evaluated. Panicking and rolling back mid-migration is how you turn a two-week dip into a six-month mess.
FAQ
How long does a site migration take for SEO? There is no fixed number. Google's John Mueller said in October 2026 that migrations can take longer than four months when Google hits problems with redirects, crawling, or understanding large-scale changes. Clean migrations on small sites are usually processed in weeks.
Should I change my URLs during a migration? Only if the new structure is clearly better. Every changed URL adds a redirect that Google must process, which adds time. And keep slugs clean: hyphens, not underscores, and do not stuff keywords into URLs; they have minimal ranking impact per Google's Gary Illyes.
What is the most common migration mistake? Weak redirect mapping. Sending everything to the homepage, leaving redirect chains, or forgetting URLs entirely. Crawl the old site first and map 1:1 301s before launch.
Do I need to keep the old domain? Keep it, and keep its redirects live, for at least a year. Dropping redirects too early is a classic way to lose the link equity you migrated.
I have handled the technical side of rebuilds like this on client projects, moving between WordPress, Shopify, and Next.js stacks. If you are planning a migration and want a second pair of eyes on the redirect map before launch, that is exactly what I do. You can find my work at https://www.shanzyseoexpert.com/ .
What is the scariest migration you have ever been through? I would genuinely like to hear the war stories.
Top comments (0)