DNS

How does DNS work?

ICANN describes the DNS as the address book of the internet. It connects a domain name to the IP address of the server behind it. When a browser needs a site, it asks a resolver, which queries the nameservers responsible for that domain and keeps the answer for a limited time. That caching is part of the design and reduces delay and load.

Common record types are A (name to IPv4 address), AAAA (name to IPv6 address), CNAME (alias to another name) and MX (mail servers).

Why does DNS matter for SEO?

If Google cannot resolve a hostname, it cannot crawl the site. The Crawl Stats report in Search Console tracks DNS resolution failures. Google’s help page treats it as an issue when DNS resolution fails for more than 5% of requests on a given day.

DNS also helps verify crawlers. Google describes a reverse DNS lookup on the IP address from your logs, which must return a hostname under googlebot.com, google.com or googleusercontent.com. A forward lookup on that hostname must then return the same IP address. Anyone can claim to be Googlebot in the user-agent string, so this check identifies fake crawlers.

Example

A zone file excerpt (the IP comes from the documentation range reserved for examples):

example.com.      A      192.0.2.10
www.example.com.  CNAME  example.com.

FAQ

Should I change my DNS server for SEO? Google does not document the public DNS resolver a visitor uses as a factor for rankings (assessment). What matters for crawling is that your authoritative nameservers answer reliably.

Last updated: October 8, 2026