A site migration is a large change to how a website is addressed or built that affects how search engines crawl and index it. Domain changes, HTTP to HTTPS moves, URL restructures, CMS or framework rebuilds and merging several sites into one all count. The aim is to carry every page's signals to its new home, which mostly comes down to redirect mapping, careful testing and close monitoring after launch.
Types of migration
Risk depends on how much changes at once. A platform swap that keeps every URL identical is lower risk than a domain move combined with new URLs, a new design and new content. Where you can, separate changes into stages so problems are easier to trace.
- Domain change, including rebrands and ccTLD consolidation
- Protocol change, such as HTTP to HTTPS
- URL structure change, such as new folder paths or slugs
- Platform or framework change, which can alter rendering and templates
- Site merge, such as folding a blog subdomain into the main site
Before launch
Crawl the current site and export every indexable URL, plus URLs with backlinks and traffic from analytics and Search Console. Build a redirect map from old to new. On staging, check templates for titles, canonicals, hreflang, structured data, robots directives and internal links, and make sure staging itself is blocked from indexing.
Launch and after
Ship the redirects as one-hop 301s or 308s, update internal links to the new URLs, publish new sitemaps, and remove any staging noindex or robots blocks. For a domain change, use Search Console's Change of Address tool. Google recommends keeping redirects in place for at least a year, and many teams keep them indefinitely.
Then monitor: crawl old URLs to confirm every one redirects correctly, watch the Page indexing and Crawl stats reports, and compare traffic by page type. Some fluctuation is normal while Google reprocesses the site; Google does not promise a timeline.
Example
Rebuilding a marketing site on a new framework
Marrowgate rebuilds its marketing site, changing frameworks and tidying URLs from /product/features/payroll to /payroll. The team exports old URLs from three sources, maps each to a new one, and tests the map on staging with a crawler. On launch day they find the blog's pagination URLs were missed and add a pattern rule within hours, because they were crawling the old URL list as soon as the release went out.
Common mistakes
Redirecting everything to the homepage
Mass homepage redirects lose page-level relevance and are often treated as soft 404s. Map each URL to its closest equivalent.
Launching with the staging noindex
A leftover noindex or robots.txt Disallow is among the most common causes of a migration traffic drop. Check headers and tags on the live site immediately.
Changing everything at once
Domain, URLs, design and content in one release make it hard to tell what caused a drop.
Questions
It varies with site size and how often Google crawls it. Google does not give a fixed period. Small sites may settle in weeks; large ones can take months.
