# DNS

Category: [Crawling & Indexing](https://seo-geo-glossary.com/en/glossary/category/crawling-indexing/) › [Crawling & crawl budget](https://seo-geo-glossary.com/en/glossary/category/crawling-indexing/crawling-crawl-budget/) · Also known as: Domain Name System

**DNS** (Domain Name System) translates domain names such as `example.com` into IP addresses so that browsers and crawlers can reach the right server. This entry covers the internet system, not the abbreviation used in biology.

## 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):

```txt
example.com.      A      192.0.2.10
www.example.com.  CNAME  example.com.
```

## Common mistakes

- Missing or wrong records after a domain or hosting move.
- Expecting a changed record to take effect everywhere at once. Cached answers expire on their own schedule.

## 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.

## Not to be confused with

- [CDN (content delivery network)](https://seo-geo-glossary.com/en/glossary/cdn/index.md): stores copies of a site on servers in several locations and delivers them from one near the visitor. DNS translates domain names into IP addresses.

## Related terms

- [Reverse DNS lookup](https://seo-geo-glossary.com/en/glossary/reverse-dns-lookup/index.md)

## Sources

- [How DNS Works – ICANN](https://www.icann.org/resources/pages/dns-2022-09-13-en)
- [Crawl Stats report – Search Console Help](https://support.google.com/webmasters/answer/9679690?hl=en)
- [Verifying Googlebot and other Google crawlers – Google Search Central](https://developers.google.com/crawling/docs/crawlers-fetchers/verify-google-requests)
- [RFC 1034: Domain Names – Concepts and Facilities (IETF)](https://www.rfc-editor.org/rfc/rfc1034.html)
- [RFC 1035: Domain Names – Implementation and Specification (IETF)](https://www.rfc-editor.org/rfc/rfc1035.html)
- [RFC 3596: DNS Extensions to Support IP Version 6 (IETF)](https://www.rfc-editor.org/rfc/rfc3596.html)

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Last updated: October 8, 2026
URL: https://seo-geo-glossary.com/en/glossary/dns/