What powers rs21.io?
Last seen Oct 2026 · 37 technologies across 19 categories
Analytics
CDN
CMS
Ecommerce
Font scripts
JavaScript frameworks
JavaScript graphics
JavaScript libraries
Marketing automation
Miscellaneous
PaaS
Performance
Programming languages
Reverse proxies
Security
Tag managers
UI frameworks
Web servers
Webmail
AI Crawlers
Restricts 16 of 33 AI crawlers we track by name in its robots.txt. Checked Oct 2026.
Training crawlers
- AI2Bot Restricted
- Applebot-Extended Restricted
- Bytespider Restricted
- CCBot Restricted
- ClaudeBot Restricted
- cohere-training-data-crawler Restricted
- FacebookBot Restricted
- Google-Extended Restricted
- GoogleOther Restricted
- GPTBot Restricted
- img2dataset Restricted
- meta-externalagent Restricted
- Webzio-Extended Restricted
Search and AI assistants
- Amazonbot Restricted
- DuckAssistBot Restricted
- YouBot Restricted
The other 17 AI crawlers we track are not mentioned and only inherit the catch-all rules that apply to every crawler.
- robots.txt found
- llms.txt not found
- ai.txt not found
AI Crawlers
16 of 33 AI crawlers restricted
Audience
United States
Where the site's Chrome visitors come from, largest estimated audience first.
Open Page Rank
3.12 / 10 · ranked #1,393,105 of all domains
36 referring domains · OpenPageRank
Core Web Vitals
| LCP | 1.4 s |
| INP | 50 ms |
| CLS | 0 |
| TTFB | 400 ms |
Real user p75, Chrome UX Report, Sep 2026.
Page
- Language: English (United States)
- Weight: 5.5 MB · 118 requests
- Structured data: JSON-LD, Microdata, OpenGraph, Twitter Cards
Homepage as crawled by the HTTP Archive, Oct 2026.
Organisation
From the homepage's own structured data (Oct 2026).
Infrastructure
- Hosted on Squarespace (198.185.159.144)
- DNS: Amazon Route 53
- Email: Microsoft 365
- Email security: SPF (hard fail), DMARC quarantine
- SSL: Let's Encrypt, RSA 2048, expires Jan 2027
- Common Crawl link graph: rank 2,086,877, 3 hosts
- Verified with: Apple Business, Google, Jamf, Microsoft 365
DNS records as swept Oct 2026, certificate as seen Oct 2026. How the web is hosted
Subdomains
| Host | Techs |
|---|---|
| rs21.io | 28 |
| www.rs21.io | 11 |
| covid.rs21.io | 7 |
Full technology history →
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Recent changes
- detected Apple iCloud Mail Jun 2026
- detected Angular Apr 2026
- detected TypeScript Apr 2026
- detected Zone.js Apr 2026