DNS Lookup Simulator

A DNS (Domain Name System) record is an instruction stored in a DNS zone file that tells DNS servers how to respond to queries for a domain. When you type a URL in your browser, DNS resolvers follow a chain of queries — from root name servers to TLD servers to authoritative name servers — to look up the matching records and return the IP address or other data needed to connect to that resource.

TTL (Time to Live) is the number of seconds a DNS record may be cached by resolvers before they must re-query the authoritative name server. A TTL of 300 means the record is cached for 5 minutes; 86400 means 24 hours. Lower TTLs allow faster propagation when you change a record but increase DNS query load. Before migrating servers, lower your A/AAAA TTL to 300 a few hours in advance so the change takes effect quickly. After migration, raise it back to 3600 or higher.

DNS propagation is not instant — it depends on the TTL of the record being changed and how aggressively resolvers around the world cache it. With a TTL of 300 (5 minutes), most resolvers will see the new value within 10–30 minutes. With a TTL of 86400 (24 hours), stale records can persist for a full day. ISP resolvers and some public DNS services may ignore TTLs and cache longer than they should. For practical purposes, allow 0–48 hours for global propagation.

An A record maps a hostname directly to an IPv4 address (e.g., example.com → 93.184.216.34). A CNAME record creates an alias from one hostname to another hostname (e.g., www.example.com → example.com). CNAME records are resolved by the client through an additional lookup. Important constraint: CNAME records cannot exist at the zone apex (the root domain itself) alongside other records like MX or NS — for this case, some DNS providers offer CNAME-flattening or ALIAS/ANAME record types.

These three TXT records form the email authentication standard. SPF (Sender Policy Framework) lists the IP addresses authorized to send email on behalf of your domain. DKIM (DomainKeys Identified Mail) publishes a public key used to verify a cryptographic signature added to outgoing emails. DMARC (Domain-based Message Authentication, Reporting, and Conformance) specifies what action receivers should take when SPF or DKIM checks fail, and where to send reports. All three are required for reliable email delivery and to avoid spam filters.

A CAA (Certification Authority Authorization) record specifies which Certificate Authorities are permitted to issue TLS/SSL certificates for your domain. Without CAA records, any trusted CA can issue a certificate for your domain. Adding CAA records is a security best practice: it prevents accidental or malicious certificate mis-issuance. For example, 'CAA 0 issue letsencrypt.org' means only Let's Encrypt can issue certificates. If you use multiple CAs, add a record for each one.