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https://w3schools.com

Sustainability

· 6 checks — CO2 emissions, green hosting, repeat-visit weight, carbon budget, and transfer efficiency rolled into one auditable list.
SCORE
74
GRADE
C
FIX
1
REVIEW
2
PASS
3
INFO
0
Device:
Mobile Desktop
Checks
6
3 PASS 2 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::
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 Amazon Web Services✗CDN Not identified✗

Based on known provider commitments. Verify at thegreenwebfoundation.org

C
Transfer Efficiency
Action
67% efficient
REVIEW
67% efficient
Warning::
Transfer efficiency: 67%
An estimated 461 KB (33%) could be eliminated: 0 KB via better compression, 0 KB via modern image formats, 461 KB of unused JavaScript. This wasted data produces 0.13g of unnecessary CO2 per page view.
67% efficient

Total waste: 461 KB (33% of page weight)

Unused JS 461 KB

0.13g unnecessary CO2 per visit

Actual transfer 1406 KB
Theoretical minimum 945 KB
Potential savings 461 KB (0.13g CO2)

See Deep Analysis sections above for specific optimizations.

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
0.39g CO2 per view
PASS
0.39g CO2 per view
Info::
0.39g CO2 per page view
This page transfers 1.4 MB, producing an estimated 0.39g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.07g, network 0.07g, end-user device 0.25g.
Got: 0.39g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 46.7 kg CO2/year
With 10,000 page views per month, this page would generate approximately 46.7 kg of CO2 annually — equivalent to charging 5836 smartphones.

0.39g

Carbon Footprint per page view

✓ Below sustainability target (0.50g)

Cleaner than 72% of websites

Sustainable Web Design model v4 · Page size: 1.4 MB

Your site
0.39g
Top 10%
0.20g
Target
0.50g
Median website
0.60g

Energy Breakdown

Data center
0.07g
Network
0.07g
End-user device
0.25g
At 10,000 monthly views: Monthly: 3.9 kg · Annual: 46.7 kg · ≈ 5836 smartphone charges
A+
Repeat Visit Weight
96% cached
PASS
96% cached
Info::
96% reduction on repeat visits
Returning visitors download only 52 KB (vs 1406 KB first visit). 44 of 46 resources are served from browser cache, saving 0.37g CO2 per repeat visit.
Info::
Repeat visit: 0.01g CO2 (first visit: 0.39g)
First visit
1406 KB
Repeat visit
52 KB

96% reduction on repeat visits

Saving 0.37g CO2 per returning visitor

44 resources served from cache · 2 resources re-downloaded

A
Carbon Budget
28th percentile
PASS
28th percentile
Info::
0.39g CO2 — below the sustainability target of 0.50g
Cleaner than an estimated 72% of websites analyzed. This page meets the Web Sustainability Guidelines target.
Info::
Estimated 28th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website

0.39g

28th percentile

Cleaner than 72% of websites

✓ Below the Web Sustainability Guidelines target

vs Median 35% cleaner ✓
vs Target 22% 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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