A naked domain is also known as a “root domain” or “apex domain”. It refers to a domain name that does not include a subdomain, such as “www“. For example, “example.com” is a naked domain, while “www.example.com“ its subdomain. A naked domain is typically the “base” domain name and can be used as the primary domain for a website, email, or other online services.
A naked domain redirect is typically required because web browsers and servers often treat naked domains and subdomains differently. For example, if a website is accessible at “www.example.com“ but not at “example.com”, then the visitors who enter the naked domain in their browser may not be able to access the website.
Domains which have unique content are recognised as authoritative domains for that content. Any other domain copying the same content are penalised by the search engines and will affect the SEO ranking of the same. Search engines treat the naked domain and subdomain as separate domains which leads to lower search engine ranking for one of the domains. Hence its a best practice to redirect naked domain to www. subdomain to make search engines understand that naked domain and www. subdomain refer to the same domain.
Lastly naked domains also have problems when websites are served via CDNs which are described here in detai
At ATOM8 we have setup the naked domain redirect using redirect.pizza as it has good free plans as well as it has A Record and CNAME based configurations. There is already a well written blog on how to set it up here.