DNS fundamentals, troubleshooting, security, and practical workflows -- written by the team that builds this tool.
Two addressing schemes, running side by side
IPv4
192.0.2.10
32 bits -- ~4.3 billion addresses -- exhausted
IPv6
2606:4700::6810:84e5
128 bits -- 340 undecillion addresses
Compare static and dynamic IP addresses, learn where each is used, and understand why domain DNS records should not be confused with a fixed address.
One hostname, several A records
1st answer
93.184.216.34
2nd answer
93.184.216.35
3rd answer
93.184.216.36
The resolver hands back every record, usually in rotating order
Learn how round robin DNS load balancing returns multiple addresses, what it can and cannot do for load distribution, and how caching affects observed results.
One hostname, several A records
1st answer
93.184.216.34
2nd answer
93.184.216.35
3rd answer
93.184.216.36
The resolver hands back every record, usually in rotating order
Compare DNS-based traffic distribution with application load balancers, and learn how TTLs, health checks, and regional answers shape availability.
Why a lookup shows the CDN, not the origin
Visitor
looks up the domain
CDN edge
104.21.x.x
this is what DNS returns
Origin server
real IP, never exposed
Learn what an origin server does behind a CDN or reverse proxy, why public DNS may show an edge address, and how to troubleshoot safely.
Why a lookup shows the CDN, not the origin
Visitor
looks up the domain
CDN edge
104.21.x.x
this is what DNS returns
Origin server
real IP, never exposed
Understand how a reverse proxy sits between clients and servers, how DNS points users to it, and how it supports routing, TLS, and security.
What is actually behind the address you resolved
Shared IP
Many sites on one address -- the Host header picks yours
Dedicated IP
Only you -- you control its reverse DNS
CDN edge
Not the origin -- the edge terminates the connection
Find the hosting IP address of a website, tell hosting from CDN endpoints, and learn what reverse DNS can and cannot tell you about the host behind an IP address.
The records you will meet in nearly every zone
Every record type worth knowing, what it does, what it looks like, and the mistake people make with it — in one reference page.
Three reasons the same domain answers differently
Geo-routing
A different edge server per region
Caching
Independent TTLs, independent caches
Split-horizon
A different answer, by design
Learn how IP geolocation estimates network location, why results can differ from a user's physical location, and what a DNS lookup can actually tell you.
Three reasons the same domain answers differently
Geo-routing
A different edge server per region
Caching
Independent TTLs, independent caches
Split-horizon
A different answer, by design
Explore geographic DNS, CDN routing, resolver caches, and split-horizon configuration to understand why a domain can return different answers.
How an email finds your mail server
Sender
you@gmail.com
MX lookup
who takes mail?
Mail server
priority 10 first
Inbox
delivered
Lowest priority number wins; higher numbers are backups
A practical guide to the DNS records email depends on, how routing and authentication work together, and what to verify after a mail migration.
How an email finds your mail server
Sender
you@gmail.com
MX lookup
who takes mail?
Mail server
priority 10 first
Inbox
delivered
Lowest priority number wins; higher numbers are backups
Check a domain's MX records, understand preference values, resolve exchanger hosts, and troubleshoot common email-routing problems.
The records you will meet in nearly every zone
Learn how wildcard DNS records match otherwise-unconfigured names, when they simplify subdomain management, and how they can hide mistakes.