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https://reference.com

Sustainability

· 6 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
2
PASS
4
INFO
0
Device:
Mobile Desktop
Checks
6
4 PASS 2 REVIEW
B
Transfer Efficiency
77% efficient
REVIEW
77% efficient
Info::
Transfer efficiency: 77%
An estimated 322 KB (23%) could be eliminated: 0 KB via better compression, 0 KB via modern image formats, 322 KB of unused JavaScript. This wasted data produces 0.07g of unnecessary CO2 per page view.
77% efficient

Total waste: 322 KB (23% of page weight)

Unused JS 322 KB

0.07g unnecessary CO2 per visit

Actual transfer 1401 KB
Theoretical minimum 1078 KB
Potential savings 322 KB (0.07g 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
0.32g CO2 per view
PASS
0.32g CO2 per view
Info::
0.32g CO2 per page view
This page transfers 1.4 MB, producing an estimated 0.32g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.01g, network 0.07g, end-user device 0.25g.
Got: 0.32g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 38.9 kg CO2/year
With 10,000 page views per month, this page would generate approximately 38.9 kg of CO2 annually — equivalent to charging 4858 smartphones.
Info::
Green hosting reduces data center emissions

0.32g

Carbon Footprint per page view

✓ Below sustainability target (0.50g)

Cleaner than 78% of websites

Sustainable Web Design model v4 · Page size: 1.4 MB

Your site
0.32g
Top 10%
0.20g
Target
0.50g
Median website
0.60g

Energy Breakdown

Data center
0.01g
Network
0.07g
End-user device
0.25g
At 10,000 monthly views: Monthly: 3.2 kg · Annual: 38.9 kg · ≈ 4858 smartphone charges
A
Green Hosting
Green (cdn)
PASS
Green (cdn)
Info::
Fastly CDN uses renewable energy
Since most traffic is served through the CDN, the majority of data transfer energy is renewable.
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 Not identified✗CDN Fastly✓

Fastly: 100% renewable energy for edge network

Based on known provider commitments. Verify at thegreenwebfoundation.org

A+
Repeat Visit Weight
94% cached
PASS
94% cached
Info::
94% reduction on repeat visits
Returning visitors download only 79 KB (vs 1401 KB first visit). 76 of 83 resources are served from browser cache, saving 0.31g CO2 per repeat visit.
Info::
Repeat visit: 0.02g CO2 (first visit: 0.32g)
First visit
1401 KB
Repeat visit
79 KB

94% reduction on repeat visits

Saving 0.31g CO2 per returning visitor

76 resources served from cache · 7 resources re-downloaded

A
Carbon Budget
22th percentile
PASS
22th percentile
Info::
0.32g CO2 — below the sustainability target of 0.50g
Cleaner than an estimated 78% of websites analyzed. This page meets the Web Sustainability Guidelines target.
Info::
Estimated 22th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website

0.32g

22nd percentile

Cleaner than 78% of websites

✓ Below the Web Sustainability Guidelines target

vs Median 46% cleaner ✓
vs Target 35% cleaner ✓
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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