Domain Health Check

Domain Health Check

One pass over everything that silently kills a domain: expiry, DNS, redirects, DNSSEC. No signup required.

Prerequisites

• dig, whois, curl (all preinstalled on macOS and most Linux)

Trigger

• "Run a domain health check on example.com"
• "When does my domain registration expire?"
• "Is http redirecting to https properly?"
• "Check DNS records for example.com"

Workflow

Set DOMAIN to the apex domain. Every command is read-only.

1. DNS record inventory:

   for t in A AAAA CNAME MX NS CAA; do echo "== $t"; dig +short "$t" "$DOMAIN"; done
   

   Evaluate:

   • No A/AAAA at apex → CRITICAL (site unreachable by name).
   • CNAME at apex → CRITICAL: forbidden alongside other apex records (RFC 1912 §2.4); breaks MX/NS resolution at many resolvers.
   • No MX → INFO if the domain sends no mail, WARN otherwise.
   • Fewer than 2 NS records, or all NS in one provider → WARN: single point of failure (RFC 2182 recommends dispersed secondaries).
   • No CAA → WARN: any CA may issue for this domain (RFC 8659 lets you pin issuers).

2. Registration expiry:

   whois "$DOMAIN" >/tmp/whois.txt 2>&1
   grep -iE 'expir|paid-through|renewal date' /tmp/whois.txt
   

   Compare the expiry date to today. Grade like a certificate: OK >30 days, WARN 8–30 days, CRITICAL ≤7 days (expired domains get parked or sniped; recovery via redemption period is slow and expensive). Registrar formats vary — if no date line matches, say so rather than guessing.

3. Redirect chain and canonicalization. Probe all four entry points:

   for u in "http://$DOMAIN/" "https://$DOMAIN/" "http://www.$DOMAIN/" "https://www.$DOMAIN/"; do
     curl -sIL -o /dev/null -m 15 -w "$u -> %{num_redirects} hops -> %{url_effective} (%{http_code})\n" "$u"
   done
   curl -sI -m 15 "http://$DOMAIN/" >/tmp/first-hop.txt
   grep -iE '^(HTTP|location)' /tmp/first-hop.txt
   

   Evaluate:

   • First hop from http:// must be a 301 to https:// — no redirect, or a 302, or an http→http hop = CRITICAL (downgrade/SEO risk).
   • More than 2 hops on any entry point → WARN: each hop adds latency and dilutes link equity.
   • www and apex must converge on ONE final URL → differing url_effective = WARN (split canonicalization; search engines index both).
   • Any final status ≠ 200 → CRITICAL.

4. DNSSEC:

   dig +short DS "$DOMAIN"
   dig +dnssec A "$DOMAIN" @1.1.1.1 >/tmp/dnssec.txt
   grep -E 'flags:|RRSIG' /tmp/dnssec.txt
   

   • DS present + ad flag from the validating resolver → OK (signed and validating).
   • No DS and no RRSIG → INFO: unsigned (common, not an error — note it).
   • DS present but no RRSIG / query returns SERVFAIL → CRITICAL: broken DNSSEC, validating resolvers (~35% of the internet) cannot reach the domain at all.

Report

## Domain Health Report: [domain]

**Overall: [OK | WARN | CRITICAL]** — worst finding wins

| Check         | Result                                   | Grade |
|---------------|------------------------------------------|-------|
| DNS records   | A:[n] AAAA:[n] MX:[n] NS:[n] CAA:[n]     | [.]   |
| Registration  | expires [date] ([N] days)                | [.]   |
| http→https    | [301 https / not redirecting / 302]      | [.]   |
| Canonical URL | [one final URL / split www vs apex]      | [.]   |
| Redirect hops | max [N] hops                             | [.]   |
| DNSSEC        | [validating / unsigned / BROKEN]         | [.]   |

### Findings
1. [CRITICAL/WARN] [finding] — [evidence] — [impact]

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