https://brew.sh
Sustainability
· 6 checks — CO2 emissions, green hosting, repeat-visit weight, carbon budget, and transfer efficiency rolled into one auditable list.SCORE
88
GRADE
B
FIX
1
REVIEW
1
PASS
4
INFO
0
Checks
64 PASS 1 REVIEW 1 FIX
DTransfer EfficiencyAction51% efficientFIX
Transfer Efficiency
Action51% efficient
51% efficient
Warning::
Transfer efficiency: 51%
An estimated 25 KB (49%) could be eliminated: 0 KB via better compression, 0 KB via modern image formats, 25 KB of unused JavaScript. This wasted data produces 0.01g of unnecessary CO2 per page view.
Total waste: 25 KB (49% of page weight)
Unused JS 25 KB
0.01g unnecessary CO2 per visit
Actual transfer 51 KB
Theoretical minimum 26 KB
Potential savings 25 KB (0.01g 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
A+CO2 Per Page Load0.01g CO2 per viewPASS
CO2 Per Page Load
0.01g CO2 per view
0.01g CO2 per view
Info::
0.01g CO2 per page view
This page transfers 0.1 MB, producing an estimated 0.01g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.00g, network 0.00g, end-user device 0.01g.
Got: 0.01g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 1.4 kg CO2/year
With 10,000 page views per month, this page would generate approximately 1.4 kg of CO2 annually — equivalent to charging 177 smartphones.
Info::
Green hosting reduces data center emissions
0.01g
Carbon Footprint per page view
✓ Below sustainability target (0.50g)
Cleaner than 90% of websites
Sustainable Web Design model v4 · Page size: 0.1 MB
Your site
0.01g
Top 10%
0.20g
Target
0.50g
Median website
0.60g
Energy Breakdown
Data center
0.00g
Network
0.00g
End-user device
0.01g
At 10,000 monthly views: Monthly: 0.1 kg · Annual: 1.4 kg · ≈ 177 smartphone charges
A+Green HostingGreen (both)PASS
Green Hosting
Green (both)
Green (both)
Info::
Both hosting and CDN use renewable energy
Got: Hosting: GitHub Pages, CDN: Fastly
Info::
GitHub Pages: Hosted on Azure/GitHub with Microsoft carbon-negative commitment
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 GitHub Pages✓CDN Fastly✓
GitHub Pages: Hosted on Azure/GitHub with Microsoft carbon-negative commitment
Fastly: 100% renewable energy for edge network
Based on known provider commitments. Verify at thegreenwebfoundation.org
A+Repeat Visit Weight89% cachedPASS
Repeat Visit Weight
89% cached
89% cached
Info::
89% reduction on repeat visits
Returning visitors download only 5 KB (vs 51 KB first visit). 7 of 8 resources are served from browser cache, saving 0.01g CO2 per repeat visit.
Info::
Repeat visit: 0.00g CO2 (first visit: 0.01g)
First visit
51 KB
Repeat visit
5 KB
89% reduction on repeat visits
Saving 0.01g CO2 per returning visitor
7 resources served from cache · 1 resources re-downloaded
A+Carbon Budget10th percentilePASS
Carbon Budget
10th percentile
10th percentile
Info::
0.01g CO2 — below the sustainability target of 0.50g
Cleaner than an estimated 90% of websites analyzed. This page meets the Web Sustainability Guidelines target.
Info::
Estimated 10th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website
0.01g
10th percentile
Cleaner than 90% of websites
✓ Below the Web Sustainability Guidelines target
vs Median 98% cleaner ✓
vs Target 98% cleaner ✓
All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.