Domain Migration & SEO (Relaunch)
An SEO-safe domain migration or website relaunch means keeping the existing URL structure of a site, or mapping every changed URL with a 301 redirect, and leaving content and internal linking untouched, so that accumulated rankings and backlink value carry over to the new domain or structure.
In practice
The most important safeguard against a drop in rankings after a relaunch is a documented URL mapping table that assigns every old URL to its new or redirected target before the launch. The sitemap, internal linking and Search Console should also be checked promptly once the move is done.