301 redirects denote that the page requested has been redirected to another page. They should be used when a page is no longer relevant, useful, or permanently deleted. They are valuable for site rebuilds, where URLs are tidied up and updated contents are added. 301 is preferred over other redirects because of its ability to pass on about 90% of link equity from the redirected pages. If a search engine bot encounters a 301 redirect when crawling your website, they remove the old URL from their index and replace it with the new one. In the meantime, visitors are also redirected to the new URL with improved infrastructure/content. If 301 redirects aren’t used when pages are permanently deleted, 404 errors are shown to the search engines and visitors. However, using an excessive number of 301 redirects when not required is not recommended.