Some of the most popular public DNS servers used by many organizations include:

• Google DNS: 8.8.8.8 and 8.8.4.4
• Cloudflare DNS: 1.1.1.1 and 1.0.0.1
• Quad9 DNS: 9.9.9.9 and 149.112.112.112
• OpenDNS: 208.67.222.222 and 208.67.220.220
• Level3 DNS: 209.244.0.3 and 209.244.0.4
• Norton ConnectSafe: 199.85.126.10 and 199.85.127.10
• Comodo Secure DNS: 8.26.56.26 and 8.20.247.20

If you wish to check your domain on less popular DNS servers, you may choose Custom from our dropdown list, and enter a fully-qualified domain name or IP address of the DNS server to retrieve results.

Every computing device on the Internet gets an IP address, and this unique IP address identifies itself and communicates with other devices. An IP address is made of 32-bit (IPv4) or 128-bit (IPv6) number, and this number is hard for humans to remember. The DNS is developed to convert the IP addresses to more memorable domain names and vice versa. There are two types of lookup that can be performed: forward lookup and reverse lookup.

The forward lookup is using a domain name to lookup an IP address. We, as humans, cannot remember lengthy numbers and therefore use domain names instead. When we visit www.google.com, the DNS lookup the domain name and returns the IP address of the corresponding domain name. This is most commonly used DNS lookup.

The reverse lookup is using an IP address to lookup a domain name. This is typically used by email servers to identify the receiving server, and filter possible spammers.

DNS records are defined in a zone file, and it contains the instructions on how to handle the DNS requests for a domain name. A DNS record mapping a domain name to an IP address or relevant information. The DNS record types include A, AAAA, CNAME, TXT, MX, NS, PTR, SRV, SOA, CAA, DS, DNSKEY and more.

• A: An address record that maps a (sub)domain name to a 32-bit IPv4 address.
• AAAA: An address record that maps a (sub)domain name to a 128-bit IPv6 address.
• CNAME: A Canonical Name (CNAME) record is used as an alias of another (sub)domain name. As an example, the www subdomain name is aliased to the main domain name.
• TXT: The TeXT (TXT) record allows an administrator to add arbitrary text in the DNS record. A TXT record may be used to verify domain authority, dnskey, dmarc,dkim, spf and other information.
• MX: The Mail Exchange (MX) records define 1 or more mail servers responsible for handling emails for the (sub)domain name. You may use our MX Validator tool to validate your MX DNS records.
• NS: The Name Server (NS) records define 1 or more name servers that are responsible for publishing DNS records for the domain name. The NS are DNS servers that are authoritative to handle the DNS query for the domain.
• PTR: A Pointer (PTR) record, points the IPv4 or IPv6 address of the host. It allows a reverse DNS lookup, which is also known as rDNS record.
• SRV: A Service (SRV) record indicates which services are offered on port numbers. Some Internet protocols such as XMPP and SIP may require SRV records.
• SOA: A Start of Authority (SOA) record provides an essential information about the domain.
• CAA: The Certification Authority Authorization (CAA) record defines the public policy regarding the issuance of digital certificates for the domain name. If no CAA record is defined, any Certification Authority can issue an SSL certificate for your domain.
• DS: The Delegation Signer (DS) record provides the unique characters of your public key and its related metadata like Key Tag, Algorithm, Digest Type and cryptographic hash value called Digest.
• DNSKEY: The DNS Key (DNSKEY) record provides public signing keys for the domain. The DS and DNSKEY records serve to validate the authenticity of DNS records returned by the DNS Server. Use our DNSKEY Lookup to serch for DNS KEY.