https://www.readingrockets.org
Sustainability
· 8 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
4
PASS
3
INFO
1
Checks
83 PASS 4 REVIEW
BCO2 Per Page Load0.63g CO2 per viewREVIEW
CO2 Per Page Load
0.63g CO2 per view
0.63g CO2 per view
Info::
0.63g CO2 per page view
This page transfers 2.7 MB, producing an estimated 0.63g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.02g, network 0.13g, end-user device 0.49g.
Got: 0.63g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 75.8 kg CO2/year
With 10,000 page views per month, this page would generate approximately 75.8 kg of CO2 annually — equivalent to charging 9476 smartphones.
Info::
Green hosting reduces data center emissions
0.63g
Carbon Footprint per page view
✗ Above sustainability target (0.50g)
Cleaner than 50% of websites
Sustainable Web Design model v4 · Page size: 2.7 MB
Your site
0.63g
Top 10%
0.20g
Target
0.50g
Median website
0.60g
Energy Breakdown
Data center
0.02g
Network
0.13g
End-user device
0.49g
At 10,000 monthly views: Monthly: 6.3 kg · Annual: 75.8 kg · ≈ 9476 smartphone charges
BCarbon Budget50th percentileREVIEW
Carbon Budget
50th percentile
50th percentile
Warning::
0.63g CO2 — above the median website (0.60g)
Heavier than an estimated 50% of websites. Reducing page weight, optimizing images, and removing unused JavaScript would lower the carbon footprint. See the Performance tab.
Info::
Estimated 50th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website
0.63g
50th percentile
Cleaner than 50% of websites
✗ Above the median website
vs Median 5% more
vs Target 26% more
BWeb Font Weight VariantsNo detectable Google Fonts weightsREVIEW
Web Font Weight Variants
No detectable Google Fonts weights
No detectable Google Fonts weights
Info::
No detectable Google Fonts weights
The analyzer detects font weights via Google Fonts URL parameters (~70% of font-using sites). Self-hosted fonts and non-Google CDN fonts aren't visible to URL-based detection. If you self-host fonts, manually audit how many @font-face weights you ship -- 2-3 weights per family is typically enough; 5+ is usually unused payload.
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
AGreen HostingGreen (cdn)PASS
Green Hosting
Green (cdn)
Green (cdn)
Info::
Cloudflare CDN uses renewable energy
Since most traffic is served through the CDN, the majority of data transfer energy is renewable.
Info::
Cloudflare: 100% renewable energy for global network since 2019
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 Platform.sh✗CDN Cloudflare✓
Cloudflare: 100% renewable energy for global network since 2019
Based on known provider commitments. Verify at thegreenwebfoundation.org
A+Repeat Visit Weight98% cachedPASS
Repeat Visit Weight
98% cached
98% cached
Info::
98% reduction on repeat visits
Returning visitors download only 50 KB (vs 2733 KB first visit). 72 of 73 resources are served from browser cache, saving 0.62g CO2 per repeat visit.
Info::
Repeat visit: 0.01g CO2 (first visit: 0.63g)
First visit
2733 KB
Repeat visit
50 KB
98% reduction on repeat visits
Saving 0.62g CO2 per returning visitor
72 resources served from cache · 1 resources re-downloaded
A+Transfer Efficiency93% efficientPASS
Transfer Efficiency
93% efficient
93% efficient
Info::
Transfer efficiency: 93%
Only 177 KB of potential savings identified. Your page is well-optimized for size.
Total waste: 177 KB (7% of page weight)
Unused JS 177 KB
0.04g unnecessary CO2 per visit
Actual transfer 2733 KB
Theoretical minimum 2555 KB
Potential savings 177 KB (0.04g CO2)
See Deep Analysis sections above for specific optimizations.
Image Optimization44 images, 1039 KB total, 55 KB wastedINFO
Image Optimization
44 images, 1039 KB total, 55 KB wasted
Image Optimization Audit
Total Images
44
Total Size
1039 KB
Oversized
3
Wasted
55 KB
2 missing dimensions 1 missing lazy loading
All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.