Definition
DNS, the Domain Name System, is the service that translates the names people type, such as a company's domain, into the numeric IP addresses that computers use to find each other. Every website visit, every email sent and every API call starts with a DNS lookup. It works as a distributed hierarchy of servers, from the root of the internet down to the provider that manages your specific domain, and the answers are cached along the way so lookups are fast.
In a company, DNS is the set of records that decide where your website loads from, which servers receive your email, which provider verifies you own the domain, and which subdomains point to which products. It lives with your domain registrar or a dedicated DNS provider. It is also a single point of failure: if your DNS is misconfigured, expired or attacked, your whole business is unreachable even though every server is running perfectly.
The misconception is that DNS is set once and forgotten. In practice, DNS records rot: old entries point to servers you no longer control, which attackers can claim, and email authentication records (SPF, DKIM and DMARC) are often missing or wrong, which sends your invoices to spam. Modern DNS providers add security features such as DNSSEC and protection against attacks, but only if someone in the company owns the configuration.
In practice
A company's website and email went dark for a day because the domain's DNS was managed from a former employee's personal account and the renewal card had expired. Every server was fine. The fix was administrative, the cost was a day of lost sales and a very awkward customer notice.
Why it matters
DNS is the one piece of infrastructure that can take down your entire company, and it is usually managed by nobody in particular. Know where your domain and DNS live, who has access, and when they renew.
Frequently asked questions
- What happens if DNS goes down?
- Your website, email and any service that uses your domain become unreachable, even though the servers themselves are still running. Users see errors or nothing at all. Because DNS answers are cached, an outage can also take hours to fully recover after it is fixed, so redundancy in DNS providers is worth considering.
- How long does a DNS change take to propagate?
- Anywhere from a few minutes to 48 hours, depending on the record's time-to-live setting and how long servers around the world cache the old value. Lowering the time-to-live in advance of a planned change makes the switch much faster. Most changes today take effect within an hour.