DNS is a hierarchical, decentralized naming system that translates human-friendly domain names into machine-routable IP addresses.
DNS (Domain Name System) is the foundational, hierarchical naming infrastructure of the global Internet, standardized in IETF RFC 1034 and RFC 1035. Often described as the "phonebook of the web," DNS translates human-memorable domain names (e.g., devflow.tools) into binary, machine-routable IPv4 (192.0.2.1) or IPv6 (2001:db8::1) network addresses required by TCP/IP routing protocols. Beyond basic address resolution, DNS powers email routing, domain ownership verification, cryptographic public-key distribution, and geo-distributed traffic balancing.
Query and troubleshoot authoritative DNS records instantly using our client-side DNS Lookup tool or trace originating hosts with IP Lookup.
| Specification | Details |
|---|---|
| Foundational Standards | IETF RFC 1034 / RFC 1035 / RFC 2181 |
| Default Network Port | Port 53 (UDP for fast queries; TCP for zone transfers or responses > 512 bytes) |
| Secure Transport Extensions | DNS over HTTPS (DoH - RFC 8484), DNS over TLS (DoT - RFC 7858), DNSSEC (RFC 4033) |
| Hierarchy Levels | Root Servers (.) → Top-Level Domain (TLD) → Authoritative Nameservers → Subdomains |
| Caching Mechanism | Time-to-Live (TTL) integer in seconds per record |
| Record | Full Name | Purpose & Primary Function | Example Value |
|---|---|---|---|
| A | Address Record | Maps a hostname to a 32-bit IPv4 address. | 93.184.216.34 |
| AAAA | IPv6 Address Record | Maps a hostname to a 128-bit IPv6 address. | 2606:2800:220:1:248:1893:25c8:1946 |
| CNAME | Canonical Name | Aliases one hostname to another canonical domain name (cannot coexist at the apex domain). | docs.example.com → example.com |
| MX | Mail Exchange | Directs inbound email to designated mail servers, prioritized by an integer preference weight. | 10 mail.example.com |
| TXT | Text Record | Carries human and machine-readable text; ubiquitous for SPF, DMARC, and domain verification tokens. | v=spf1 include:_spf.google.com ~all |
| NS | Name Server | Delegates a DNS zone to authoritative nameservers. | ns1.cloudflare.com |
| PTR | Pointer Record | Resolves an IP address back to a hostname (Reverse DNS lookup). | 34.216.184.93.in-addr.arpa |
| CAA | Certification Authority Authorization | Restricts which Certificate Authorities (CAs) are authorized to issue SSL/TLS certificates for the domain. | 0 issue "letsencrypt.org" |
When a client browser navigates to an uncached URL, the resolution journey follows a recursive lookup tree:
Client Browser ──> 1. DNS Recursive Resolver (ISP / 1.1.1.1)
│
├──> 2. Root Nameserver (.)
│
├──> 3. TLD Nameserver (.tools)
│
└──> 4. Authoritative Nameserver (Host Provider)
│
▼ Returns IP: 104.21.45.10
1.1.1.1 or Google 8.8.8.8). If the answer is cached locally in memory within the record's TTL window, it returns immediately..): If uncached, the resolver queries one of the 13 root server clusters worldwide, which directs the request to the TLD nameservers..com or .org) replies with the authoritative nameservers responsible for the specific domain.A or AAAA), which the resolver caches and hands back to the browser to initiate the HTTP/TLS handshake.dns/promises)import { promises as dns } from 'dns';
async function inspectDomainRecords(domain: string) {
try {
// Resolve IPv4 addresses
const ipv4 = await dns.resolve4(domain);
console.log(`A Records for ${domain}:`, ipv4);
// Resolve Mail Exchange (MX) records
const mxRecords = await dns.resolveMx(domain);
console.log('MX Records:', mxRecords);
// Resolve TXT records for SPF/DMARC inspection
const txtRecords = await dns.resolveTxt(domain);
console.log('TXT Records:', txtRecords.flat());
} catch (error) {
console.error(`DNS Resolution failed: ${(error as Error).message}`);
}
}
inspectDomainRecords('wtool.dev');
TTL is an integer value specified in seconds that instructs intermediate DNS caches and client resolvers how long they are permitted to cache a record before querying authoritative servers again. Lowering TTL to 300 seconds (5 minutes) before planned server migrations ensures rapid traffic redirection.
Per RFC 1912, a CNAME record cannot coexist with any other record type for the same hostname. Because a root apex domain (e.g., example.com) inherently requires SOA and NS records, placing a CNAME at the apex creates an RFC violation. Modern DNS providers offer workarounds called CNAME Flattening or ALIAS records.
DNS propagation delays can cause different geographic regions to see stale records. Use our live DNS Lookup Tool to query live records against authoritative resolvers.
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