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https://universiteitleiden.nl

Sustainability

· 6 checks — CO2 emissions, green hosting, repeat-visit weight, carbon budget, and transfer efficiency rolled into one auditable list.
SCORE
77
GRADE
C
FIX
1
REVIEW
3
PASS
2
INFO
0
Device:
Mobile Desktop
Checks
6
2 PASS 3 REVIEW 1 FIX
D
Green Hosting
Action
Unknown
FIX
Unknown
Info::
Hosting provider could not be identified
Without knowing the provider, we cannot determine their energy sourcing. Check with your hosting provider about their renewable energy commitments.
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 HostingUnable to Determine
Hosting Not identified✗CDN Not identified✗

Based on known provider commitments. Verify at thegreenwebfoundation.org

B
Carbon Budget
32th percentile
REVIEW
32th percentile
Info::
0.42g CO2 — below the sustainability target of 0.50g
Cleaner than an estimated 68% of websites analyzed. This page meets the Web Sustainability Guidelines target.
Info::
Estimated 32th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website

0.42g

32nd percentile

Cleaner than 68% of websites

✓ Below the Web Sustainability Guidelines target

vs Median 30% cleaner ✓
vs Target 16% cleaner ✓
B
Transfer Efficiency
87% efficient
REVIEW
87% efficient
Info::
Transfer efficiency: 87%
An estimated 199 KB (13%) could be eliminated: 0 KB via better compression, 0 KB via modern image formats, 199 KB of unused JavaScript. This wasted data produces 0.06g of unnecessary CO2 per page view.
87% efficient

Total waste: 199 KB (13% of page weight)

Unused JS 199 KB

0.06g unnecessary CO2 per visit

Actual transfer 1525 KB
Theoretical minimum 1326 KB
Potential savings 199 KB (0.06g CO2)

See Deep Analysis sections above for specific optimizations.

C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A
CO2 Per Page Load
0.42g CO2 per view
PASS
0.42g CO2 per view
Info::
0.42g CO2 per page view
This page transfers 1.5 MB, producing an estimated 0.42g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.08g, network 0.07g, end-user device 0.27g.
Got: 0.42g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 50.6 kg CO2/year
With 10,000 page views per month, this page would generate approximately 50.6 kg of CO2 annually — equivalent to charging 6326 smartphones.

0.42g

Carbon Footprint per page view

✓ Below sustainability target (0.50g)

Cleaner than 68% of websites

Sustainable Web Design model v4 · Page size: 1.5 MB

Your site
0.42g
Top 10%
0.20g
Target
0.50g
Median website
0.60g

Energy Breakdown

Data center
0.08g
Network
0.07g
End-user device
0.27g
At 10,000 monthly views: Monthly: 4.2 kg · Annual: 50.6 kg · ≈ 6326 smartphone charges
A+
Repeat Visit Weight
100% cached
PASS
100% cached
Info::
100% reduction on repeat visits
Returning visitors download only 7 KB (vs 1525 KB first visit). 38 of 40 resources are served from browser cache, saving 0.42g CO2 per repeat visit.
Info::
Repeat visit: 0.00g CO2 (first visit: 0.42g)
First visit
1525 KB
Repeat visit
7 KB

100% reduction on repeat visits

Saving 0.42g CO2 per returning visitor

38 resources served from cache · 2 resources re-downloaded

All checks on this page are automated. Results are estimates - run targeted manual reviews when the score affects a release decision.

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