Skip to content
https://kotlinlang.org

Sustainability

· 6 checks — CO2 emissions, green hosting, repeat-visit weight, carbon budget, and transfer efficiency rolled into one auditable list.
SCORE
64
GRADE
D
FIX
3
REVIEW
2
PASS
1
INFO
0
Device:
Mobile Desktop
Checks
6
1 PASS 2 REVIEW 3 FIX
D
CO2 Per Page Load
Action
1.09g CO2 per view
FIX
1.09g CO2 per view
Warning::
1.09g CO2 per page view
This page transfers 3.9 MB, producing an estimated 1.09g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.20g, network 0.19g, end-user device 0.70g.
Got: 1.09g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 131.3 kg CO2/year
With 10,000 page views per month, this page would generate approximately 131.3 kg of CO2 annually — equivalent to charging 16409 smartphones.

1.09g

Carbon Footprint per page view

✗ Above sustainability target (0.50g)

Cleaner than 36% of websites

Sustainable Web Design model v4 · Page size: 3.9 MB

Your site
1.09g
Top 10%
0.20g
Target
0.50g
Median website
0.60g

Energy Breakdown

Data center
0.20g
Network
0.19g
End-user device
0.70g
At 10,000 monthly views: Monthly: 10.9 kg · Annual: 131.3 kg · ≈ 16409 smartphone charges
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

D
Carbon Budget
Action
64th percentile
FIX
64th percentile
Warning::
1.09g CO2 — above the median website (0.60g)
Heavier than an estimated 36% of websites. Reducing page weight, optimizing images, and removing unused JavaScript would lower the carbon footprint. See the Performance tab.
Info::
Estimated 64th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website

1.09g

64th percentile

Cleaner than 36% of websites

✗ Above the median website

vs Median 82% more
vs Target 119% more
B
Transfer Efficiency
83% efficient
REVIEW
83% efficient
Info::
Transfer efficiency: 83%
An estimated 664 KB (17%) could be eliminated: 0 KB via better compression, 0 KB via modern image formats, 664 KB of unused JavaScript. This wasted data produces 0.18g of unnecessary CO2 per page view.
83% efficient

Total waste: 664 KB (17% of page weight)

Unused JS 664 KB

0.18g unnecessary CO2 per visit

Actual transfer 3955 KB
Theoretical minimum 3291 KB
Potential savings 664 KB (0.18g 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+
Repeat Visit Weight
97% cached
PASS
97% cached
Info::
97% reduction on repeat visits
Returning visitors download only 99 KB (vs 3955 KB first visit). 152 of 155 resources are served from browser cache, saving 1.07g CO2 per repeat visit.
Info::
Repeat visit: 0.03g CO2 (first visit: 1.09g)
First visit
3955 KB
Repeat visit
99 KB

97% reduction on repeat visits

Saving 1.07g CO2 per returning visitor

152 resources served from cache · 3 resources re-downloaded

All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.

Send Feedback