Question 1

What DNS record types does dnsfyi check?

Accepted Answer

dnsfyi checks A, AAAA, CNAME, MX, TXT, NS, SOA, CAA, and PTR records simultaneously across multiple global resolvers.

Question 2

Why do DNS resolvers return different answers?

Accepted Answer

Resolvers may return different answers due to DNS propagation delays (changes take time to replicate globally), geographic GeoDNS routing (different IPs for different regions), or stale TTL caches in intermediate servers.

Question 3

What is DNS TTL and why does it matter?

Accepted Answer

TTL (Time To Live) is the number of seconds a DNS record can be cached by resolvers. A low TTL (e.g., 60s) means changes propagate quickly but increases DNS query load. A high TTL (e.g., 86400s = 24h) reduces load but slows propagation. Before a planned migration, lower your TTL to 300s (5 min) at least 24 hours in advance.

Question 4

What is a CNAME record and when should I use it?

Accepted Answer

A CNAME (Canonical Name) record maps one domain name to another. For example, www.example.com → example.com. You cannot use a CNAME on the root apex domain (@) — use an A record or ALIAS/ANAME record instead. Many providers like Cloudflare support CNAME flattening at the apex.

Question 5

What is a CAA record?

Accepted Answer

A CAA (Certification Authority Authorization) record specifies which Certificate Authorities (CAs) are allowed to issue SSL/TLS certificates for your domain. For example, '0 issue letsencrypt.org' restricts issuance to Let's Encrypt only, reducing the risk of misissued certificates.

Question 6

How do I check DNS propagation?

Accepted Answer

Use the DNS Propagation Checker to monitor how your DNS changes are spreading across global resolvers in real time. Propagation typically takes 1–48 hours depending on your previous TTL value.