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Infrastructure

· 9 checks — DNS, redirects, IPv6, crawlability, URL variants, and domain intelligence rolled into one auditable list.
SCORE
90
GRADE
A
FIX
1
REVIEW
3
PASS
5
INFO
0
Probed from Madrid, Spain
200 OK
Checks
9
5 PASS 3 REVIEW 1 FIX
D
CDN & Delivery
Action
No CDN detected
FIX
No CDN detected
Warning::
No CDN detected
A CDN can significantly improve load times for users around the world by caching content at edge nodes closer to them.
No CDN detected

Consider using a CDN to improve global delivery speed and reduce origin load.

B
Crawlability
no robots.txt, no sitemap
REVIEW
no robots.txt, no sitemap
Info::
No robots.txt found
robots.txt is optional but recommended. It tells search engine crawlers which pages to index.
Info::
No sitemap.xml found
A sitemap helps search engines discover and index your pages more efficiently.

robots.txt is optional but recommended. It tells search engine crawlers which pages to index.

Why this matters

No robots.txt — crawlers fetch /robots.txt and get 404; not breaking but means default crawl behavior with no directives or sitemap reference.

Learn more

A minimal robots.txt with `User-agent: * / Allow: / / Sitemap: https://example.com/sitemap.xml` covers the basics. Without it, crawlers behave fine but lose the sitemap signal and can't be selectively blocked from crawl-traps.

Source: robotstxt.org

A sitemap helps search engines discover and index your pages more efficiently.

Why this matters

No sitemap.xml — Google relies on crawl-graph discovery alone, slowing indexing of deep or fresh URLs.

Learn more

A sitemap accelerates Google's discovery of new and updated content. Most CMSes auto-generate one; static-site frameworks need a build-step plugin. Reference it from robots.txt and submit in Search Console to confirm Google can fetch it.

Source: sitemaps.org / Google Search Central

robots.txt No robots.txt found

No robots.txt found

This is fine for most sites — a missing robots.txt allows all crawling by default.

sitemap.xml No sitemap found

No sitemap found

Adding a sitemap helps search engines discover your pages.

B
URL Variants
www/non-www, trailing slash, HTTP→HTTPS
REVIEW
www/non-www, trailing slash, HTTP→HTTPS
Critical::
Both www and non-www versions serve content
Got: Both variants return 200 Expected: One variant 301-redirects to the other
Info::
HTTP correctly 301-redirects to HTTPS

www / non-www

200https://www.calibre-ebook.com/
200https://calibre-ebook.com/

Inconsistent — duplicate content risk

HTTP → HTTPS

301http://calibre-ebook.com/ https://calibre-ebook.com/

Consistent

B
TLS Certificate Expiry & Recommendations
86 days until leaf cert expires — 3 issues to address
REVIEW

Certificate validity

86
days left
0d 30d 60d 90d+

Recommended actions

  • Enable HSTS: Strict-Transport-Security: max-age=31536000; includeSubDomains
  • Enable DNSSEC on your domain for DNS spoofing protection
  • Enable OCSP stapling on your TLS server to remove a CA roundtrip and protect user privacy
A
DNS Records
1 A records, 52 ms lookup
PASS
1 A records, 52 ms lookup
Info::
Resolves to 1 IPv4 address(es)
Got: 15.204.223.162
Info::
Single A record — no DNS redundancy
Multiple A records provide failover if one server goes down.
Info::
Has 1 IPv6 (AAAA) record(s)
Got: 2604:2dc0:101:200::9e4
Info::
2 nameserver(s) configured
Got: ns45.domaincontrol.com, ns46.domaincontrol.com
Info::
No MX records — email not configured via DNS
Info::
CAA records not checked
CAA record lookup requires a specialized DNS resolver. This check will be available in a future update.
Info::
No SPF record found in TXT records
SPF helps prevent email spoofing. Add a TXT record starting with 'v=spf1'.
Info::
DNS resolution time: 52 ms
Got: 52 ms
A15.204.223.162
AAAA2604:2dc0:101:200::9e4
CNAME
NSns45.domaincontrol.com, ns46.domaincontrol.com
MX
TXT
CAALookup not available with standard resolver
Resolved in 52 ms

Multiple A records provide failover if one server goes down.

Why this matters

Single A record means a single point of failure — if that IP goes down, your site is unreachable until DNS TTL expires.

Learn more

Add multiple A records for round-robin failover, or use a managed DNS provider with health-checked failover (Route 53, Cloudflare, NS1). Short TTL (60-300s) lets clients recover faster on outages.

Source: SRE practice / DNS architecture

CAA record lookup requires a specialized DNS resolver. This check will be available in a future update.

Why this matters

Informational: CAA (Certification Authority Authorization) records weren't checked in this scan.

SPF helps prevent email spoofing. Add a TXT record starting with 'v=spf1'.

Why this matters

Without SPF, receiving servers can't validate sending IPs — your domain is easier to spoof in phishing.

Learn more

SPF complements DMARC. Both should be published. SPF records list authorized sending IPs (e.g., `v=spf1 include:_spf.google.com ~all` for Google Workspace). After publishing, verify in Google Postmaster Tools or mxtoolbox.

Source: RFC 7208 (SPF)

A+
Redirect Chain
No redirects — direct access
PASS
No redirects — direct access
Info::
No redirects — direct access
Got: https://calibre-ebook.com

https://calibre-ebook.com

298 ms · HTTP/1.1 FINAL

#URLStatusTimeProtocolServer
1https://calibre-ebook.com200298 msHTTP/1.1nginx
A+
IPv6 Readiness
IPv6 reachable (95 ms)
PASS
IPv6 reachable (95 ms)
Info::
IPv6 is configured and reachable at 2604:2dc0:101:200::9e4
Got: 95 ms connect
IPv6 Ready
AAAA Records 2604:2dc0:101:200::9e4 Connection Reachable (95 ms)
A+
Domain Intelligence
calibre-ebook.com — via GoDaddy.com, LLC, 17 years, 3 months old
PASS
calibre-ebook.com — via GoDaddy.com, LLC, 17 years, 3 months old
Info::
Domain registered until Mar 24, 2028 (1 years, 11 months remaining)
Info::
DNSSEC is not enabled
DNSSEC protects against DNS spoofing attacks. While not required, enabling DNSSEC adds an additional layer of security. Contact your DNS provider to enable it.
Info::
Registrar: GoDaddy.com, LLC
Warning::
Registrar lock is NOT enabled
The domain can be transferred without an unlock step. Enable registrar lock (clientTransferProhibited) in your registrar's control panel to protect against unauthorized or accidental transfers.
Domain expiry

648 days

March 24, 2028

SSL certificate

86 days

Issued by Let's Encrypt

Domain age

17 years, 3 months

Registered March 24, 2009

DNSSEC

Not enabled

Protects against DNS spoofing

Hosting

Unknown

2604:2dc0:101:200::9e4

Registrar

GoDaddy.com, LLC

Unlocked 2 NS records
Expiry timeline
Today
+1 year
Domain expiry SSL expiry Danger zone (≤30 days)
Recommended actions
  • Enable DNSSEC to protect visitors from DNS spoofing
  • Enable registrar lock (clientTransferProhibited) to block unauthorized domain transfers
Registrar GoDaddy.com, LLC
Created March 24, 2009 (17 years, 3 months ago)
Expires March 24, 2028 (1 years, 11 months)
Last Updated March 25, 2026
Name Servers ns45.domaincontrol.com, ns46.domaincontrol.com
DNSSEC Not enabled
Hosting
IP Address 2604:2dc0:101:200::9e4
Data source: rdap (0.1s)

DNSSEC protects against DNS spoofing attacks. While not required, enabling DNSSEC adds an additional layer of security. Contact your DNS provider to enable it.

Why this matters

Without DNSSEC, an attacker who can poison your DNS can hijack your domain — and SSL certs alone don't stop them.

Learn more

DNSSEC adds cryptographic signatures to DNS records, preventing forged responses from poisoning resolver caches. Without it, an attacker who controls the network path can redirect your domain to a malicious server before any HTTPS handshake happens. Most modern registrars (Cloudflare, Google Domains, Route 53) enable it with one toggle.

Source: ICANN / RFC 4033

The domain can be transferred without an unlock step. Enable registrar lock (clientTransferProhibited) in your registrar's control panel to protect against unauthorized or accidental transfers.

Why this matters

Without registrar lock, an attacker who phishes your registrar credentials can transfer the domain in minutes — total brand hijack.

Learn more

Registrar lock (clientTransferProhibited, clientUpdateProhibited, clientDeleteProhibited) requires extra verification before any transfer/update/delete. Every major registrar offers it free. Combined with 2FA on your registrar account, it's the strongest defense against domain hijacking.

Source: ICANN / domain-security best practice

A+
HTTP Probe Timing
Total 355 ms — DNS, TCP, TLS, TTFB, content transfer breakdown
PASS
DNS Lookup DNS Lookup — time to resolve the domain name to an IP address.
56 ms
TCP Connect TCP Connect — time to establish a TCP connection to the server.
94 ms
TLS Handshake TLS Handshake — time to complete the HTTPS encryption handshake.
110 ms
Time to First Byte Time to First Byte — how long the server takes to respond with the first byte of data.
355 ms
Total Time Total request time from DNS lookup through full response.
355 ms

Connection waterfall

DNS Lookup 56 ms TCP Connect 94 ms TLS Handshake 110 ms Server Processing 95 ms Content Transfer 0 ms
All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.

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