DNS Lookup

What Is a DNS Lookup?

A DNS lookup queries the Domain Name System to retrieve the DNS records associated with a domain name. DNS is the internet's phone book — it translates human-readable domain names like github.com into the IP addresses that computers use to communicate. The Toolsiro DNS Lookup tool queries Google's or Cloudflare's DNS-over-HTTPS (DoH) resolvers to retrieve real-time DNS records for any domain, supporting ten record types including A, AAAA, MX, NS, TXT, CNAME, SOA, CAA, SRV, and more.

DNS Record Types — What Each One Does

• A record (Address): Maps a domain name to an IPv4 address. The most fundamental DNS record — it tells browsers which server to connect to when they request your website. A domain can have multiple A records pointing to different servers for load balancing or failover.
• AAAA record (IPv6 Address): The IPv6 equivalent of an A record. Maps a domain to a 128-bit IPv6 address. Increasingly important as IPv4 addresses become scarcer. Many modern hosting providers serve both A and AAAA records.
• MX record (Mail Exchange): Specifies the mail servers responsible for receiving email for the domain. MX records include a priority value — lower numbers mean higher priority. If a domain has multiple MX records, email is delivered to the highest-priority server first, falling back to lower-priority servers if the first is unavailable.
• NS record (Name Server): Identifies the authoritative name servers for the domain — the servers that hold the definitive DNS records. NS records are set at the domain registrar and tell the internet where to look up all other DNS records for that domain.
• TXT record (Text): Stores arbitrary text data. Used for a wide variety of purposes: SPF records (authorised email senders), DKIM keys (email authentication signatures), DMARC policies (email fraud prevention), domain ownership verification for Google Search Console, SSL certificate validation (ACME challenges), and more.
• CNAME record (Canonical Name): Creates an alias from one domain name to another. For example, www.example.com might be a CNAME pointing to example.com. Commonly used to point subdomains to the root domain, or to map custom domains to hosting provider addresses (e.g., pointing to a Netlify or Vercel deployment URL).
• SOA record (Start of Authority): Contains administrative information about the DNS zone — the primary name server, the email address of the zone administrator (with @ replaced by .), and several timing parameters (serial number, refresh, retry, expire, minimum TTL). Every DNS zone has exactly one SOA record.
• CAA record (Certification Authority Authorisation): Specifies which Certificate Authorities (CAs) are permitted to issue SSL/TLS certificates for the domain. Prevents unauthorised certificate issuance. For example, a CAA record can restrict certificate issuance to Let's Encrypt only, blocking other CAs from issuing certificates even if they are technically capable.
• SRV record (Service): Specifies the location (hostname and port) of servers for specific services. Used by protocols like SIP (VoIP), XMPP (instant messaging), and Microsoft services. SRV records include priority, weight, port, and target fields.

What Is TTL?

Every DNS record includes a TTL (Time To Live) value measured in seconds. TTL tells DNS resolvers and caches how long to store the record before querying the authoritative server again. The Toolsiro tool displays TTL values in human-readable format (e.g., 5m for 300 seconds, 1h for 3600 seconds).

• Low TTL (60–300 seconds): Changes propagate quickly — useful when you plan to update DNS records soon, or when running a migration.
• High TTL (3600–86400 seconds): Reduces DNS query load and speeds up website loading for users. Best for stable records that rarely change.
• TTL 0: No caching — every DNS query goes directly to the authoritative server. Very rarely used in production.

DNS-over-HTTPS (DoH) — What It Means

Traditional DNS queries are sent in plain text over UDP port 53, visible to your ISP, network administrator, or anyone monitoring your traffic. DNS-over-HTTPS (DoH) encrypts DNS queries inside HTTPS connections, making them indistinguishable from regular web traffic. The Toolsiro DNS Lookup tool uses DoH exclusively — all queries are encrypted before leaving your browser. You can choose between Google's public resolver (dns.google) and Cloudflare's resolver (cloudflare-dns.com), both of which support DoH and are free to use.

Common DNS Lookup Use Cases

• Verifying DNS propagation: After updating DNS records, use the lookup tool to confirm the new records are live. Note that DNS caching may mean changes take up to 48 hours to propagate globally, though most updates are visible within minutes to a few hours.
• Email configuration troubleshooting: Check MX records to verify which mail servers handle a domain's email, and check TXT records for SPF, DKIM, and DMARC configurations that affect deliverability.
• Debugging website connectivity issues: Check A and AAAA records to confirm a domain points to the correct IP address after a server migration or hosting change.
• SSL certificate troubleshooting: Check CAA records to determine which CAs are authorised to issue certificates, and check TXT records for ACME challenges during certificate issuance.
• Investigating domain configuration: Check NS records to determine which DNS provider a domain uses (Cloudflare, Route53, Google Cloud DNS, etc.).
• Subdomain discovery: Look up CNAME records to see where subdomains point — useful for understanding a domain's infrastructure.

Related Network Tools

The DNS Lookup tool works best alongside Whois Lookup for complete domain investigation — Whois shows registration and ownership data while DNS Lookup shows live technical configuration. For IP-level geographic information, use IP Geolocation.