redzilla
Topic

Diagnostics

DNS, WHOIS, ports and email health.

Learn first

DNS & Network Troubleshooting How a name really resolves, what to check when “the page won’t load”, and how to verify SPF/DKIM/DMARC so your mail stays out of spam. ≈ 12 min read →

8 tools

DNS Lookup

Query DNS records (A, AAAA, MX, TXT, NS, PTR…) over DNS-over-HTTPS.

WHOIS / RDAP

Look up registration data for domains, IPs and ASNs via RDAP, the modern WHOIS.

My IP / IP Info

Show your public IP and everything about an IP: ASN, organization, geolocation, time zone and reverse DNS.

Port Checker

Check whether one or more TCP ports are open on a host, as seen from the internet. Handy for verifying firewall rules.

Reverse PTR Zone

Generate in-addr.arpa / ip6.arpa names and sample PTR zone lines from an IP or CIDR (IPv4/IPv6).

CIDR to Regex & Range

Convert a CIDR subnet into a regular expression matching its IPs and into the address range, for log filtering and ACLs.

SPF / DKIM / DMARC

Look up and explain a domain email-authentication records (SPF, DMARC and DKIM) over DNS-over-HTTPS.

DNS Propagation

Query a DNS record on several public resolvers (Cloudflare, Google) and compare answers to see if it has propagated.