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Sustainability

· 6 checks — CO2 emissions, green hosting, repeat-visit weight, carbon budget, and transfer efficiency rolled into one auditable list.
SCORE
83
GRADE
B
FIX
0
REVIEW
2
PASS
4
INFO
0
Device:
Mobile Desktop
Checks
6
4 PASS 2 REVIEW
C
Transfer Efficiency
Action
72% efficient
REVIEW
72% efficient
Warning::
Transfer efficiency: 72%
An estimated 406 KB (28%) could be eliminated: 0 KB via better compression, 0 KB via modern image formats, 406 KB of unused JavaScript. This wasted data produces 0.09g of unnecessary CO2 per page view.
72% efficient

Total waste: 406 KB (28% of page weight)

Unused JS 406 KB

0.09g unnecessary CO2 per visit

Actual transfer 1450 KB
Theoretical minimum 1043 KB
Potential savings 406 KB (0.09g 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
0.34g CO2 per view
PASS
0.34g CO2 per view
Info::
0.34g CO2 per page view
This page transfers 1.4 MB, producing an estimated 0.34g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.01g, network 0.07g, end-user device 0.26g.
Got: 0.34g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 40.2 kg CO2/year
With 10,000 page views per month, this page would generate approximately 40.2 kg of CO2 annually — equivalent to charging 5027 smartphones.
Info::
Green hosting reduces data center emissions

0.34g

Carbon Footprint per page view

✓ Below sustainability target (0.50g)

Cleaner than 77% of websites

Sustainable Web Design model v4 · Page size: 1.4 MB

Your site
0.34g
Top 10%
0.20g
Target
0.50g
Median website
0.60g

Energy Breakdown

Data center
0.01g
Network
0.07g
End-user device
0.26g
At 10,000 monthly views: Monthly: 3.4 kg · Annual: 40.2 kg · ≈ 5027 smartphone charges
A
Green Hosting
Green (cdn)
PASS
Green (cdn)
Info::
Fastly CDN uses renewable energy
Since most traffic is served through the CDN, the majority of data transfer energy is renewable.
Info::
Heroku: Runs on AWS; renewable status depends on region
Info::
Fastly: 100% renewable energy for edge network
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 Hosting✓ Green Hosted
Hosting Heroku✗CDN Fastly✓

Heroku: Runs on AWS; renewable status depends on region

Fastly: 100% renewable energy for edge network

Based on known provider commitments. Verify at thegreenwebfoundation.org

A+
Repeat Visit Weight
97% cached
PASS
97% cached
Info::
97% reduction on repeat visits
Returning visitors download only 47 KB (vs 1450 KB first visit). 58 of 60 resources are served from browser cache, saving 0.32g CO2 per repeat visit.
Info::
Repeat visit: 0.01g CO2 (first visit: 0.34g)
First visit
1450 KB
Repeat visit
47 KB

97% reduction on repeat visits

Saving 0.32g CO2 per returning visitor

58 resources served from cache · 2 resources re-downloaded

A
Carbon Budget
23th percentile
PASS
23th percentile
Info::
0.34g CO2 — below the sustainability target of 0.50g
Cleaner than an estimated 77% of websites analyzed. This page meets the Web Sustainability Guidelines target.
Info::
Estimated 23th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website

0.34g

23rd percentile

Cleaner than 77% of websites

✓ Below the Web Sustainability Guidelines target

vs Median 44% cleaner ✓
vs Target 33% 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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