DNS Issues vs Website Downtime: How to Tell the Difference
If a website looks down, it might be DNS rather than the server itself. DNS errors prevent users from finding the server, while true downtime means the server is found but fails to respond. This guide helps you tell the difference quickly.
Short definition
DNS issues mean the domain does not resolve correctly. Website downtime means DNS resolves but the server returns errors or timeouts.
Signs it is a DNS issue
NXDOMAIN (name does not exist)
NXDOMAIN means the domain name in the query does not exist from the authoritative server. That is a DNS issue, not a web server issue.
SERVFAIL (server failure)
SERVFAIL indicates the name server could not process the query due to a DNS server problem. This points to DNS infrastructure.
Inconsistent results across resolvers
If one resolver returns the correct IP and another does not, you likely have DNS propagation or caching issues.
Recent DNS changes + TTL delays
DNS records are cached for their TTL. Changes can take time to reach all users, which creates partial availability.
Signs it is true website downtime
5xx errors
If DNS resolves and you see 500/503 errors, the server is found but failing to fulfill requests.
Timeouts after DNS resolves
If the IP address is correct but the connection times out, the origin server or network path is failing.
Same failure from multiple networks
If different ISPs and locations see the same failure, it is likely a real outage.
Partial outages on key endpoints
The homepage might load, but checkout or login fails. That is still downtime for affected users.
Fast tests to tell the difference
- Resolve the domain using two different public resolvers.
- Check whether DNS returns NXDOMAIN or SERVFAIL.
- If DNS resolves, request the URL and note 200 vs 5xx vs timeout.
- Compare results from another network or device.
- Review recent DNS changes and TTL values.
Quick DNS checks (commands)
# Check DNS with a public resolver nslookup yourdomain.com 1.1.1.1 nslookup yourdomain.com 8.8.8.8 # Dig for detailed status (ANSWER, AUTHORITY, NXDOMAIN) dig yourdomain.com @1.1.1.1 dig yourdomain.com @8.8.8.8
How to reduce DNS-related downtime
Lower TTL before major changes
Shorter TTLs reduce propagation delays when you move servers or update IP addresses.
Monitor DNS separately
Track DNS resolution in addition to HTTP uptime so you can distinguish DNS failures quickly.
Use multi-location checks
Multi-location monitoring helps catch regional DNS failures.
Keep records clean
Remove stale records (like old AAAA or A records) after migrations.
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FAQ
Does NXDOMAIN always mean the domain is gone?
It means the authoritative server says the name does not exist. That is usually a DNS misconfiguration or expired domain.
Can DNS issues be intermittent?
Yes. Caching and resolver behavior can create inconsistent results across regions.
What is SERVFAIL?
SERVFAIL indicates a DNS server failure when processing the query.
Is a 503 error a DNS problem?
No. A 503 indicates the server is reachable but temporarily unable to handle requests.
Sources
RFC 1035: DNS response codes define SERVFAIL (server failure) and Name Error (NXDOMAIN).
RFC 2308: negative caching TTL for NXDOMAIN responses is derived from the SOA record and controls how long resolvers cache failures.
Cloudflare DNS TTL docs: TTL controls how long records are cached and how long updates take to reach end users.
RFC 7231: 503 Service Unavailable indicates temporary overload or maintenance at the server.