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astralcodexten.com

Astral Codex Ten | Scott Alexander | Substack

Last scanned Aug 4, 2026, 10:00 AM · 14 views

86

Overall score

Great

Summary

P(A|B) = [P(A)*P(B|A)]/P(B), all the rest is commentary. This website uses Express behind Cloudflare CDN. SEO is excellent (90/100) and accessibility is excellent (100/100). Security scores good (85/100) and performance fair (70/100). Top issue: robots.txt not found.

P(A|B) = [P(A)*P(B|A)]/P(B), all the rest is commentary. Click to read Astral Codex Ten, by Scott Alexander, a Substack publication.

Top issues to fix

6 issues found · 1 high priority

  • Slow estimated load (4.6s)

    Performance

    Use a CDN, enable caching/compression, and cut render-blocking assets — every extra second costs conversions.

  • Missing X-Content-Type-Options header

    Security

    Add X-Content-Type-Options: nosniff to stop MIME-sniffing attacks.

  • Missing X-Frame-Options header

    Security

    Add X-Frame-Options (or a CSP frame-ancestors rule) to prevent clickjacking via hidden iframes.

  • robots.txt not found

    SEO

    Publish /robots.txt with a Sitemap: directive to guide crawlers.

  • sitemap.xml not found

    SEO

    Publish an XML sitemap and reference it from robots.txt to speed up page discovery.

  • 20 broken links on the page

    SEO

    Fix or remove broken links — they waste crawl budget and erode user trust.

90

SEO

2 issue(s) found

70

Performance

4.60 s

85

Security

HTTPS & header checks

100

Accessibility

0 issue(s) found

Score history

-5 overall since Jul 27, 2026

Overall
86
SEO
90
Security
85
Performance
70
Accessibility
100

Organization

Company details published in this site's own structured data.

P(A|B) = [P(A)*P(B|A)]/P(B), all the rest is commentary. Click to read Astral Codex Ten, by Scott Alexander, a Substack publication.

Meta tags

Title
Astral Codex Ten | Scott Alexander | Substack
Description
P(A|B) = [P(A)*P(B|A)]/P(B), all the rest is commentary. Click to read Astral Codex Ten, by Scott Alexander, a Substack publication.
Canonical
https://www.astralcodexten.com/
Language
en
Charset
utf-8
Viewport
width=device-width, initial-scale=1, maximum-scale=1, user-scalable=0, viewport-fit=cover
Robots meta
Manifest

OpenGraph & Twitter Card

OpenGraph

og:title
Astral Codex Ten | Scott Alexander | Substack
og:description
P(A|B) = [P(A)*P(B|A)]/P(B), all the rest is commentary. Click to read Astral Codex Ten, by Scott Alexander, a Substack publication.
og:type
article
og:url
https://www.astralcodexten.com/

Twitter Card

twitter:card
summary_large_image
twitter:title
Astral Codex Ten | Scott Alexander | Substack
twitter:description
P(A|B) = [P(A)*P(B|A)]/P(B), all the rest is commentary. Click to read Astral Codex Ten, by Scott Alexander, a Substack publication.

Technologies

Detected frameworks, languages, and tools.

Hosting & CDN

Hosting provider
CDN provider
Cloudflare
IP address
ASN

DNS records

TypeValue
A
AAAA
MX
TXT
NS
CAA
CNAME
IPv6 supportNo

TLS / SSL certificate

Version
TLS 1.3
Issuer
Google Trust Services
Subject
www.astralcodexten.com
Valid from
Jul 14, 2026
Valid to
Oct 12, 2026
Days until expiry
69
SAN domains
www.astralcodexten.com

Security headers

  • Strict-Transport-SecurityEnabled
  • Content-Security-PolicyEnabled
  • X-Frame-OptionsMissing
  • X-Content-Type-OptionsMissing
  • Referrer-PolicyMissing
  • Permissions-PolicyMissing

Compression: gzip · 3 cookie(s) observed

Content & assets

Headings

H1 1 · H2 0 · H3 0

Links

14 internal · 24 external · 20 broken

Images

15 total · 0 missing alt

Scripts / Styles

173 scripts · 20 stylesheets

JS / CSS size

232 KB · 1.8 KB

Page size

374 KB

Robots.txt & Sitemap

robots.txt
Not found
Disallow rules
0
sitemap.xml
Not found
URLs in sitemap
0

SEO issues

  • robots.txt not found
  • sitemap.xml not found

Accessibility issues

No accessibility issues detected.

Scan details

Requested URL
https://astralcodexten.com
Final URL
https://www.astralcodexten.com/
HTTP status
200
HTTP version
HTTP/2
Response time
4.59 s
HTML size
374 KB
Redirect chain
https://astralcodexten.com → https://www.astralcodexten.com/

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Frequently asked questions

What technology does astralcodexten.com use?
astralcodexten.com is built with Express, Node.js, Cloudflare Analytics.
Is astralcodexten.com secure (HTTPS)?
Yes. astralcodexten.com uses TLS 1.3 with a certificate issued by Google Trust Services, valid until Oct 12, 2026.
Who hosts astralcodexten.com?
Hosting provider information for astralcodexten.com is not available yet.
What is astralcodexten.com's SEO score?
astralcodexten.com scored 90/100 for SEO in the latest analysis (excellent).
What is astralcodexten.com's overall website score?
astralcodexten.com has an overall SiteGraph score of 86/100, combining SEO, performance, security, and accessibility.
Has astralcodexten.com's score changed over time?
astralcodexten.com's overall score has declined by 5 points (from 91 to 86) since Jul 27, 2026.