Skip to content
https://english-heritage.org.uk

Sustainability

· 6 checks — CO2 emissions, green hosting, repeat-visit weight, carbon budget, and transfer efficiency rolled into one auditable list.
SCORE
69
GRADE
D
FIX
2
REVIEW
2
PASS
2
INFO
0
Device:
Mobile Desktop
Checks
6
2 PASS 2 REVIEW 2 FIX
D
CO2 Per Page Load
Action
1.50g CO2 per view
FIX
1.50g CO2 per view
Warning::
1.50g CO2 per page view
This page transfers 6.3 MB, producing an estimated 1.50g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.04g, network 0.31g, end-user device 1.15g.
Got: 1.50g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 179.9 kg CO2/year
With 10,000 page views per month, this page would generate approximately 179.9 kg of CO2 annually — equivalent to charging 22486 smartphones.
Info::
Green hosting reduces data center emissions

1.50g

Carbon Footprint per page view

✗ Above sustainability target (0.50g)

Cleaner than 25% of websites

Sustainable Web Design model v4 · Page size: 6.3 MB

Your site
1.50g
Top 10%
0.20g
Target
0.50g
Median website
0.60g

Energy Breakdown

Data center
0.04g
Network
0.31g
End-user device
1.15g
At 10,000 monthly views: Monthly: 15.0 kg · Annual: 179.9 kg · ≈ 22486 smartphone charges
F
Carbon Budget
Action
75th percentile
FIX
75th percentile
Warning::
1.50g CO2 — above the median website (0.60g)
Heavier than an estimated 25% of websites. Reducing page weight, optimizing images, and removing unused JavaScript would lower the carbon footprint. See the Performance tab.
Info::
Estimated 75th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website

1.50g

75th percentile

Cleaner than 25% of websites

✗ Above the median website

vs Median 150% more
vs Target 200% more
B
Transfer Efficiency
88% efficient
REVIEW
88% efficient
Info::
Transfer efficiency: 88%
An estimated 771 KB (12%) could be eliminated: 0 KB via better compression, 0 KB via modern image formats, 771 KB of unused JavaScript. This wasted data produces 0.18g of unnecessary CO2 per page view.
88% efficient

Total waste: 771 KB (12% of page weight)

Unused JS 771 KB

0.18g unnecessary CO2 per visit

Actual transfer 6485 KB
Theoretical minimum 5713 KB
Potential savings 771 KB (0.18g 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
Green Hosting
Green (cdn)
PASS
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::
Azure: Microsoft is carbon-negative; Azure renewable varies by region
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 Azure✗CDN Cloudflare✓

Azure: Microsoft is carbon-negative; Azure renewable varies by region

Cloudflare: 100% renewable energy for global network since 2019

Based on known provider commitments. Verify at thegreenwebfoundation.org

A+
Repeat Visit Weight
100% cached
PASS
100% cached
Info::
100% reduction on repeat visits
Returning visitors download only 18 KB (vs 6485 KB first visit). 96 of 100 resources are served from browser cache, saving 1.49g CO2 per repeat visit.
Info::
Repeat visit: 0.00g CO2 (first visit: 1.50g)
First visit
6485 KB
Repeat visit
18 KB

100% reduction on repeat visits

Saving 1.49g CO2 per returning visitor

96 resources served from cache · 4 resources re-downloaded

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

Send Feedback