Site moves and redirect signals

Google treats 301/308 (and instant meta refresh) as permanent redirects and a strong signal that the target is canonical; 302/307 are temporary, a weak signal, and the source may stay in results. For a site move Google advises an old-to-new URL map, server-side permanent redirects kept for at least a year, updated canonicals, hreflang and sitemaps, Change of Address only for domain or subdomain moves, and chains ideally no more than 3 hops (Googlebot follows up to 10). Redirecting many old URLs to one irrelevant URL such as the home page may be treated as a soft 404.