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https://zachbloss.com

Sustainability

· 7 checks — CO2 emissions, green hosting, repeat-visit weight, carbon budget, and transfer efficiency rolled into one auditable list.
SCORE
81
GRADE
B
FIX
1
REVIEW
3
PASS
3
INFO
0
Device:
Mobile Desktop
Checks
7
3 PASS 3 REVIEW 1 FIX
D
Green Hosting
Action
Not green
FIX
Not green
Info::
No confirmed renewable energy commitment detected
Consider providers like Cloudflare, Google Cloud, or Vercel that match 100% of their energy use with renewables.
Info::
AWS: Renewable energy varies by region; committed to 100% by 2025
Info::
AWS CloudFront: Renewable varies by edge location
Info::
Green hosting status based on known provider commitments
Green hosting detection uses a curated database of provider renewable energy commitments. This is not a real-time verification. For authoritative checks, visit thegreenwebfoundation.org.
Green HostingNot Green Hosted
Hosting AWS✗CDN AWS CloudFront✗

AWS: Renewable energy varies by region; committed to 100% by 2025

AWS CloudFront: Renewable varies by edge location

Based on known provider commitments. Verify at thegreenwebfoundation.org

C
Transfer Efficiency
Action
71% efficient
REVIEW
71% efficient
Warning::
Transfer efficiency: 71%
An estimated 84 KB (29%) could be eliminated: 0 KB via better compression, 0 KB via modern image formats, 84 KB of unused JavaScript. This wasted data produces 0.02g of unnecessary CO2 per page view.
71% efficient

Total waste: 84 KB (29% of page weight)

Unused JS 84 KB

0.02g unnecessary CO2 per visit

Actual transfer 291 KB
Theoretical minimum 206 KB
Potential savings 84 KB (0.02g CO2)

See Deep Analysis sections above for specific optimizations.

B
Web Font Weight Variants
No detectable Google Fonts weights
REVIEW
No detectable Google Fonts weights
Info::
No detectable Google Fonts weights
The analyzer detects font weights via Google Fonts URL parameters (~70% of font-using sites). Self-hosted fonts and non-Google CDN fonts aren't visible to URL-based detection. If you self-host fonts, manually audit how many @font-face weights you ship -- 2-3 weights per family is typically enough; 5+ is usually unused payload.
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A+
CO2 Per Page Load
0.08g CO2 per view
PASS
0.08g CO2 per view
Info::
0.08g CO2 per page view
This page transfers 0.3 MB, producing an estimated 0.08g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.01g, network 0.01g, end-user device 0.05g.
Got: 0.08g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 9.7 kg CO2/year
With 10,000 page views per month, this page would generate approximately 9.7 kg of CO2 annually — equivalent to charging 1207 smartphones.

0.08g

Carbon Footprint per page view

✓ Below sustainability target (0.50g)

Cleaner than 90% of websites

Sustainable Web Design model v4 · Page size: 0.3 MB

Your site
0.08g
Top 10%
0.20g
Target
0.50g
Median website
0.60g

Energy Breakdown

Data center
0.01g
Network
0.01g
End-user device
0.05g
At 10,000 monthly views: Monthly: 0.8 kg · Annual: 9.7 kg · ≈ 1207 smartphone charges
A+
Repeat Visit Weight
99% cached
PASS
99% cached
Info::
99% reduction on repeat visits
Returning visitors download only 2 KB (vs 291 KB first visit). 14 of 15 resources are served from browser cache, saving 0.08g CO2 per repeat visit.
Info::
Repeat visit: 0.00g CO2 (first visit: 0.08g)
First visit
291 KB
Repeat visit
2 KB

99% reduction on repeat visits

Saving 0.08g CO2 per returning visitor

14 resources served from cache · 1 resources re-downloaded

A+
Carbon Budget
10th percentile
PASS
10th percentile
Info::
0.08g CO2 — below the sustainability target of 0.50g
Cleaner than an estimated 90% of websites analyzed. This page meets the Web Sustainability Guidelines target.
Info::
Estimated 10th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website

0.08g

10th percentile

Cleaner than 90% of websites

✓ Below the Web Sustainability Guidelines target

vs Median 87% cleaner ✓
vs Target 84% cleaner ✓
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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