https://www.stackoverflow.blog
Sustainability
· 6 checks — CO2 emissions, green hosting, repeat-visit weight, carbon budget, and transfer efficiency rolled into one auditable list.SCORE
87
GRADE
B
FIX
0
REVIEW
2
PASS
4
INFO
0
Checks
64 PASS 2 REVIEW
BTransfer Efficiency88% efficientREVIEW
Transfer Efficiency
88% efficient
88% efficient
Info::
Transfer efficiency: 88%
An estimated 147 KB (12%) could be eliminated: 0 KB via better compression, 0 KB via modern image formats, 147 KB of unused JavaScript. This wasted data produces 0.03g of unnecessary CO2 per page view.
Total waste: 147 KB (12% of page weight)
Unused JS 147 KB
0.03g unnecessary CO2 per visit
Actual transfer 1269 KB
Theoretical minimum 1121 KB
Potential savings 147 KB (0.03g CO2)
See Deep Analysis sections above for specific optimizations.
CGreen HostingActionWhether the site is served from green-energy infrastructureREVIEW
Green Hosting
ActionWhether the site is served from green-energy infrastructure
Green Hosting
No green hosting detected
ACO2 Per Page Load0.29g CO2 per viewPASS
CO2 Per Page Load
0.29g CO2 per view
0.29g CO2 per view
Info::
0.29g CO2 per page view
This page transfers 1.2 MB, producing an estimated 0.29g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.01g, network 0.06g, end-user device 0.23g.
Got: 0.29g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 35.2 kg CO2/year
With 10,000 page views per month, this page would generate approximately 35.2 kg of CO2 annually — equivalent to charging 4400 smartphones.
Info::
Green hosting reduces data center emissions
0.29g
Carbon Footprint per page view
✓ Below sustainability target (0.50g)
Cleaner than 81% of websites
Sustainable Web Design model v4 · Page size: 1.2 MB
Your site
0.29g
Top 10%
0.20g
Target
0.50g
Median website
0.60g
Energy Breakdown
Data center
0.01g
Network
0.06g
End-user device
0.23g
At 10,000 monthly views: Monthly: 2.9 kg · Annual: 35.2 kg · ≈ 4400 smartphone charges
AGreen HostingGreen (cdn)PASS
Green Hosting
Green (cdn)
Green (cdn)
Info::
Netlify CDN uses renewable energy
Since most traffic is served through the CDN, the majority of data transfer energy is renewable.
Info::
Netlify: Hosted on AWS/Google Cloud with renewable energy matching
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 Not identified✗CDN Netlify✓
Netlify: Hosted on AWS/Google Cloud with renewable energy matching
Based on known provider commitments. Verify at thegreenwebfoundation.org
A+Repeat Visit Weight95% cachedPASS
Repeat Visit Weight
95% cached
95% cached
Info::
95% reduction on repeat visits
Returning visitors download only 66 KB (vs 1269 KB first visit). 76 of 78 resources are served from browser cache, saving 0.28g CO2 per repeat visit.
Info::
Repeat visit: 0.02g CO2 (first visit: 0.29g)
First visit
1269 KB
Repeat visit
66 KB
95% reduction on repeat visits
Saving 0.28g CO2 per returning visitor
76 resources served from cache · 2 resources re-downloaded
ACarbon Budget19th percentilePASS
Carbon Budget
19th percentile
19th percentile
Info::
0.29g CO2 — below the sustainability target of 0.50g
Cleaner than an estimated 81% of websites analyzed. This page meets the Web Sustainability Guidelines target.
Info::
Estimated 19th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website
0.29g
19th percentile
Cleaner than 81% of websites
✓ Below the Web Sustainability Guidelines target
vs Median 51% cleaner ✓
vs Target 41% cleaner ✓
All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.