https://knihobot.cz
Sustainability
· 8 checks — CO2 emissions, green hosting, repeat-visit weight, carbon budget, and transfer efficiency rolled into one auditable list.SCORE
65
GRADE
D
FIX
3
REVIEW
3
PASS
1
INFO
1
Checks
81 PASS 3 REVIEW 3 FIX
DGreen HostingActionNot greenFIX
Green Hosting
ActionNot green
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::
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 Next.js✗CDN Not identified✗
Based on known provider commitments. Verify at thegreenwebfoundation.org
DCarbon BudgetAction52th percentileFIX
Carbon Budget
Action52th percentile
52th percentile
Warning::
0.69g CO2 — above the median website (0.60g)
Heavier than an estimated 48% of websites. Reducing page weight, optimizing images, and removing unused JavaScript would lower the carbon footprint. See the Performance tab.
Info::
Estimated 52th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website
0.69g
52nd percentile
Cleaner than 48% of websites
✗ Above the median website
vs Median 15% more
vs Target 38% more
FTransfer EfficiencyAction37% efficientFIX
Transfer Efficiency
Action37% efficient
37% efficient
Critical::
Transfer efficiency: 37%
An estimated 1570 KB (63%) could be eliminated: 0 KB via better compression, 0 KB via modern image formats, 1570 KB of unused JavaScript. This wasted data produces 0.43g of unnecessary CO2 per page view.
Total waste: 1570 KB (63% of page weight)
Unused JS 1570 KB
0.43g unnecessary CO2 per visit
Actual transfer 2499 KB
Theoretical minimum 929 KB
Potential savings 1570 KB (0.43g CO2)
See Deep Analysis sections above for specific optimizations.
BCO2 Per Page Load0.69g CO2 per viewREVIEW
CO2 Per Page Load
0.69g CO2 per view
0.69g CO2 per view
Info::
0.69g CO2 per page view
This page transfers 2.4 MB, producing an estimated 0.69g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.13g, network 0.12g, end-user device 0.44g.
Got: 0.69g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 83.0 kg CO2/year
With 10,000 page views per month, this page would generate approximately 83.0 kg of CO2 annually — equivalent to charging 10371 smartphones.
0.69g
Carbon Footprint per page view
✗ Above sustainability target (0.50g)
Cleaner than 48% of websites
Sustainable Web Design model v4 · Page size: 2.4 MB
Your site
0.69g
Top 10%
0.20g
Target
0.50g
Median website
0.60g
Energy Breakdown
Data center
0.13g
Network
0.12g
End-user device
0.44g
At 10,000 monthly views: Monthly: 6.9 kg · Annual: 83.0 kg · ≈ 10371 smartphone charges
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
A+Repeat Visit Weight99% cachedPASS
Repeat Visit Weight
99% cached
99% cached
Info::
99% reduction on repeat visits
Returning visitors download only 35 KB (vs 2499 KB first visit). 160 of 161 resources are served from browser cache, saving 0.68g CO2 per repeat visit.
Info::
Repeat visit: 0.01g CO2 (first visit: 0.69g)
First visit
2499 KB
Repeat visit
35 KB
99% reduction on repeat visits
Saving 0.68g CO2 per returning visitor
160 resources served from cache · 1 resources re-downloaded
Image Optimization24 images, 240 KB total, 109 KB wastedINFO
Image Optimization
24 images, 240 KB total, 109 KB wasted
Image Optimization Audit
Total Images
24
Total Size
240 KB
Oversized
4
Wasted
109 KB
1 missing alt text 14 missing dimensions 11 missing lazy loading
All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.