A 301 redirect is an HTTP status code that tells browsers and search engines a page has permanently moved to a new URL. When applied to an expired domain, it forwards all visitors and roughly 90% of the domain's link equity to your target site. It's the fastest way to transfer an expired domain's SEO value without rebuilding the old site.
How 301 redirects work
When a browser requests a URL that has a 301 redirect, the server responds with the new location. The browser automatically follows the redirect. Search engines do the same thing, but they also pass most of the original page's authority to the destination. Google has confirmed that 301 redirects transfer PageRank, though some small amount is lost in the process.
You can set up a 301 at the server level (Apache .htaccess, Nginx config) or through your DNS provider. The redirect can be domain-wide (everything on old-domain.com goes to new-domain.com) or page-by-page (old-domain.com/about goes to new-domain.com/about). Page-level redirects preserve more value because the content relevance is maintained.
Using 301 redirects with expired domains
Buying an expired domain and 301-redirecting it to your site is a go-to strategy in SEO. It works best when the expired domain is topically related to your site. A retired French bakery domain redirected to your bakery website makes sense. That same domain redirected to a tech blog won't transfer as much value because the backlinks aren't relevant to the new content.
There are risks. If the expired domain had spammy or toxic backlinks, you're redirecting that toxicity to your own site. Always check the backlink profile and Trust Flow before redirecting. The Wayback history matters too. And keep in mind that Google can devalue redirects it considers manipulative, especially if you're redirecting dozens of unrelated domains to a single site.