https://unsplash.com
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 Efficiency85% efficientREVIEW
Transfer Efficiency
85% efficient
85% efficient
Info::
Transfer efficiency: 85%
An estimated 218 KB (15%) could be eliminated: 0 KB via better compression, 0 KB via modern image formats, 218 KB of unused JavaScript. This wasted data produces 0.05g of unnecessary CO2 per page view.
Total waste: 218 KB (15% of page weight)
Unused JS 218 KB
0.05g unnecessary CO2 per visit
Actual transfer 1479 KB
Theoretical minimum 1261 KB
Potential savings 218 KB (0.05g 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 Load0.34g CO2 per viewPASS
CO2 Per Page Load
0.34g CO2 per view
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: 41.0 kg CO2/year
With 10,000 page views per month, this page would generate approximately 41.0 kg of CO2 annually — equivalent to charging 5131 smartphones.
Info::
Green hosting reduces data center emissions
0.34g
Carbon Footprint per page view
✓ Below sustainability target (0.50g)
Cleaner than 76% 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: 41.0 kg · ≈ 5131 smartphone charges
AGreen HostingGreen (cdn)PASS
Green Hosting
Green (cdn)
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::
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 Not identified✗CDN Fastly✓
Fastly: 100% renewable energy for edge network
Based on known provider commitments. Verify at thegreenwebfoundation.org
A+Repeat Visit Weight94% cachedPASS
Repeat Visit Weight
94% cached
94% cached
Info::
94% reduction on repeat visits
Returning visitors download only 88 KB (vs 1479 KB first visit). 79 of 80 resources are served from browser cache, saving 0.32g CO2 per repeat visit.
Info::
Repeat visit: 0.02g CO2 (first visit: 0.34g)
First visit
1479 KB
Repeat visit
88 KB
94% reduction on repeat visits
Saving 0.32g CO2 per returning visitor
79 resources served from cache · 1 resources re-downloaded
ACarbon Budget24th percentilePASS
Carbon Budget
24th percentile
24th percentile
Info::
0.34g CO2 — below the sustainability target of 0.50g
Cleaner than an estimated 76% of websites analyzed. This page meets the Web Sustainability Guidelines target.
Info::
Estimated 24th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website
0.34g
24th percentile
Cleaner than 76% of websites
✓ Below the Web Sustainability Guidelines target
vs Median 43% cleaner ✓
vs Target 32% cleaner ✓
All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.