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 BudgetAction51th percentileFIX
Carbon Budget
Action51th percentile
51th percentile
Warning::
0.65g CO2 — above the median website (0.60g)
Heavier than an estimated 49% of websites. Reducing page weight, optimizing images, and removing unused JavaScript would lower the carbon footprint. See the Performance tab.
Info::
Estimated 51th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website
0.65g
51st percentile
Cleaner than 49% of websites
✗ Above the median website
vs Median 9% more
vs Target 31% more
DTransfer EfficiencyAction46% efficientFIX
Transfer Efficiency
Action46% efficient
46% efficient
Critical::
Transfer efficiency: 46%
An estimated 1268 KB (54%) could be eliminated: 0 KB via better compression, 0 KB via modern image formats, 1268 KB of unused JavaScript. This wasted data produces 0.35g of unnecessary CO2 per page view.
Total waste: 1268 KB (54% of page weight)
Unused JS 1268 KB
0.35g unnecessary CO2 per visit
Actual transfer 2360 KB
Theoretical minimum 1092 KB
Potential savings 1268 KB (0.35g CO2)
See Deep Analysis sections above for specific optimizations.
BCO2 Per Page Load0.65g CO2 per viewREVIEW
CO2 Per Page Load
0.65g CO2 per view
0.65g CO2 per view
Info::
0.65g CO2 per page view
This page transfers 2.3 MB, producing an estimated 0.65g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.12g, network 0.11g, end-user device 0.42g.
Got: 0.65g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 78.3 kg CO2/year
With 10,000 page views per month, this page would generate approximately 78.3 kg of CO2 annually — equivalent to charging 9792 smartphones.
0.65g
Carbon Footprint per page view
✗ Above sustainability target (0.50g)
Cleaner than 49% of websites
Sustainable Web Design model v4 · Page size: 2.3 MB
Your site
0.65g
Top 10%
0.20g
Target
0.50g
Median website
0.60g
Energy Breakdown
Data center
0.12g
Network
0.11g
End-user device
0.42g
At 10,000 monthly views: Monthly: 6.5 kg · Annual: 78.3 kg · ≈ 9792 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 2360 KB first visit). 127 of 128 resources are served from browser cache, saving 0.64g CO2 per repeat visit.
Info::
Repeat visit: 0.01g CO2 (first visit: 0.65g)
First visit
2360 KB
Repeat visit
35 KB
99% reduction on repeat visits
Saving 0.64g CO2 per returning visitor
127 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.