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https://www.substack.com

Infrastructure

· 9 checks — DNS, redirects, IPv6, crawlability, URL variants, and domain intelligence rolled into one auditable list.
SCORE
92
GRADE
A
FIX
0
REVIEW
2
PASS
7
INFO
0
Probed from Madrid, Spain
301 Moved Permanently
Checks
9
7 PASS 2 REVIEW
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.substack.com/
200https://substack.com/

Inconsistent — duplicate content risk

HTTP → HTTPS

301http://www.substack.com/ → https://www.substack.com/

Consistent

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

Certificate validity

77
days left
0d 30d 60d 90d+

Recommended actions

  • Submit your domain to hstspreload.org to be added to the Chrome preload list
  • 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
2 A records, 33 ms lookup
PASS
2 A records, 33 ms lookup
Info::
Resolves to 2 IPv4 address(es)
Got: 104.18.37.200, 172.64.150.56
Info::
Has 2 IPv6 (AAAA) record(s)
Got: 2606:4700:4400::ac40:9638, 2606:4700:440b::6812:25c8
Info::
No NS records found
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: 33 ms
Got: 33 ms
A104.18.37.200, 172.64.150.56
AAAA2606:4700:4400::ac40:9638, 2606:4700:440b::6812:25c8
CNAME—
NS—
MX—
TXT—
CAALookup not available with standard resolver
Resolved in 33 ms

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
1 redirect(s), 386 ms total
PASS
1 redirect(s), 386 ms total
Info::
Single redirect
Got: https://www.substack.com → https://substack.com/ (301)
Info::
WWW normalization redirect

https://www.substack.com

162 ms · HTTP/1.1

301

https://substack.com/

224 ms · HTTP/1.1 FINAL

#URLStatusTimeProtocolServer
1https://www.substack.com301162 msHTTP/1.1cloudflare
2https://substack.com/200224 msHTTP/1.1cloudflare

See the visual redirect chain in the HTTP Probe tab →

A+
IPv6 Readiness
IPv6 reachable (17 ms)
PASS
IPv6 reachable (17 ms)
Info::
IPv6 is configured and reachable at 2606:4700:4400::ac40:9638, 2606:4700:440b::6812:25c8
Got: 17 ms connect
IPv6 Ready
AAAA Records 2606:4700:4400::ac40:9638, 2606:4700:440b::6812:25c8 Connection Reachable (17 ms)
A+
Crawlability
robots.txt present, sitemap with 11 URLs
PASS
robots.txt present, sitemap with 11 URLs
Info::
robots.txt is present
Got: 587 bytes
Info::
sitemap.xml is present
Info::
sitemap.xml is valid XML
Info::
sitemap.xml contains 11 entries
Info::
Sitemap index with 11 child sitemaps
Info::
robots.txt references sitemap
robots.txt 200 OK
Size 587 B Sitemaps referenced 2 User-agents BLEXBot, Twitterbot, *, facebookexternalhit Blocking No — crawling allowed
User-agent: BLEXBot
Disallow: /

User-agent: Twitterbot
Disallow:



User-agent: *
Disallow: /action/
Disallow: /publish
Disallow: /sign-in
Disallow: /channel-frame
Disallow: /session-attribution-frame
Disallow: /visited-surface-frame
Disallow: /feed/private
Disallow: /feed/podcast/*/private/*.rss
Disallow: /subscribe
Disallow: /lovestack/*
Disallow: /p/*/comment/*
Disallow: /inbox/post/*
Disallow: /notes/post/*
Disallow: /embed



User-agent: facebookexternalhit
Allow: /
Allow: /subscribe


SITEMAP: https://substack.com/sitemap.xml
SITEMAP: https://substack.com/news_sitemap.xml
sitemap.xml 200 OK
Type Sitemap Index URLs 11 entries Valid XML Yes
Child Sitemaps:
A+
Domain Intelligence
substack.com — via Amazon Registrar, Inc., 16 years, 2 months old
PASS
substack.com — via Amazon Registrar, Inc., 16 years, 2 months old
Info::
Domain registered until Apr 27, 2030 (4 years, 1 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: Amazon Registrar, Inc.
Domain expiry

1385 days

April 27, 2030

SSL certificate

77 days

Issued by Google Trust Services

Domain age

16 years, 2 months

Registered April 27, 2010

DNSSEC

Not enabled

Protects against DNS spoofing

Hosting

Unknown

2606:4700:440b::6812:25c8

Registrar

Amazon Registrar, Inc.

Lock status unknown 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
Registrar Amazon Registrar, Inc.
Created April 27, 2010 (16 years, 2 months ago)
Expires April 27, 2030 (4 years, 1 months)
Last Updated January 5, 2023
Name Servers ali.ns.cloudflare.com, lee.ns.cloudflare.com
DNSSEC Not enabled
Hosting
IP Address 2606:4700:440b::6812:25c8
Data source: rdap (0.2s)

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

A+
HTTP Probe Timing
Total 201 ms — DNS, TCP, TLS, TTFB, content transfer breakdown
PASS
DNS Lookup DNS Lookup — time to resolve the domain name to an IP address.
41 ms
TCP Connect TCP Connect — time to establish a TCP connection to the server.
17 ms
TLS Handshake TLS Handshake — time to complete the HTTPS encryption handshake.
21 ms
Time to First Byte Time to First Byte — how long the server takes to respond with the first byte of data.
201 ms
Total Time Total request time from DNS lookup through full response.
202 ms

Connection waterfall

DNS Lookup 41 ms TCP Connect 17 ms TLS Handshake 21 ms Server Processing 123 ms Content Transfer 0 ms
A
CDN & Delivery
Cloudflare (DYNAMIC)
PASS
Cloudflare (DYNAMIC)
Info::
Site is served via Cloudflare CDN (edge: CDG)
Got: cf-ray: 9e8bbaa44ab6ebac-CDG
Info::
CDN cache status: DYNAMIC
CDN Detected: Cloudflare
Provider Cloudflare Cache Status DYNAMIC Evidence cf-ray: 9e8bbaa44ab6ebac-CDG
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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