is it DNS?

Check a domain that is not working: whether the name resolves in public DNS, then the eleven-check audit of its zone, each row ok, warn, fail or skipped with why. DNS only, not HTTP or TLS, and not for one record: dig. Measured from the isitdns edge and its probes, never the caller's network. from moves the recursion, TTL and UDP truncation rows to that region's probe.

check_domain

Dig one name and type at one board resolver, or at Cloudflare, Google, Quad9 and AdGuard side by side (resolver all): records, flags, rcode, EDE, latency. Not for a whole domain: check_domain. Asked over DoH from the isitdns edge. from moves the question to that region's probe as Do53 over UDP, and follow: true adds the CNAME chain as separate reads with DNSSEC off. A resolver given as an address must be on the board.

dig

Read a domain's registration from its registry's RDAP server: each status with what it means for resolution, the registration, expiry and change dates, the nameservers, whether the delegation is signed. Not for what DNS answers: check_domain. Read over HTTPS from the isitdns edge through IANA's RDAP bootstrap, and no contacts are returned. A hostname is read at the name, then each parent down to the registered domain, and each HTTP read is listed with its URL, status and time.

registration

Sweep a zone's nameservers: the same names and types asked at a sample of its authoritative addresses, reporting disagreements, lame or silent servers, serial and TTL differences, the CAA in effect, and each _acme-challenge TXT or CNAME. Not for a public resolver's answer: dig. Asked with RD=0 over TCP from the isitdns edge or a probe, named on each answer. Every question not asked is listed with why, and an answer past 22,000 bytes is trimmed with counts, the whole sweep at its api: URL. names are labels under domain (@ for domain itself), 16 at most, and types 8 at most.

sweep_domain

Trace a delegation from the root to the authority, like dig +trace: each referral and its glue, the one server that answered at each zone cut and any dial that failed, the final answer and its TTLs. Not for every server of a zone: sweep_domain. Each hop is asked with RD=0 over TCP from the isitdns edge or a probe, named on the hop. Give the full host name: the walk ends at the zone that answers for it, and type (default A) is what it asks there.

trace

Walk the DNSSEC chain from the root to one answer: DS and DNSKEY at each signed zone cut, key tags, signers, signature windows, and the first link that breaks or goes insecure. Not for one signed record: dig. Read through Cloudflare's resolver over DoH with CD=1 from the isitdns edge, and a key set a break would rest on again through Google's. Signature bytes are not verified, so a clean walk does not prove the answer validates. type (default A) is the record checked at the end, not OPT, RRSIG or a meta type such as ANY.

dnssec_chain