Skip to content
https://nationalgallery.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
0
PASS
4
INFO
0
Device:
Mobile Desktop
Checks
6
4 PASS 2 FIX
F
CO2 Per Page Load
Action
4.08g CO2 per view
FIX
4.08g CO2 per view
Critical::
4.08g CO2 per page view
This page transfers 17.2 MB, producing an estimated 4.08g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.10g, network 0.84g, end-user device 3.13g.
Got: 4.08g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 489.6 kg CO2/year
With 10,000 page views per month, this page would generate approximately 489.6 kg of CO2 annually — equivalent to charging 61196 smartphones.
Info::
Green hosting reduces data center emissions

4.08g

Carbon Footprint per page view

✗ Above sustainability target (0.50g)

Cleaner than 5% of websites

Sustainable Web Design model v4 · Page size: 17.2 MB

Your site
4.08g
Top 10%
0.20g
Target
0.50g
Median website
0.60g

Energy Breakdown

Data center
0.10g
Network
0.84g
End-user device
3.13g
At 10,000 monthly views: Monthly: 40.8 kg · Annual: 489.6 kg · ≈ 61196 smartphone charges
F
Carbon Budget
Action
95th percentile
FIX
95th percentile
Warning::
4.08g CO2 — above the median website (0.60g)
Heavier than an estimated 5% of websites. Reducing page weight, optimizing images, and removing unused JavaScript would lower the carbon footprint. See the Performance tab.
Info::
Estimated 95th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website

4.08g

95th percentile

Cleaner than 5% of websites

✗ Above the median website

vs Median 580% more
vs Target 716% more
A+
Green Hosting
Green (both)
PASS
Green (both)
Info::
Both hosting and CDN use renewable energy
Got: Hosting: Cloudflare, CDN: Cloudflare
Info::
Cloudflare: Verified by the Green Web Foundation
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 Cloudflare✓CDN Cloudflare✓

Cloudflare: Verified by the Green Web Foundation

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 26 KB (vs 17650 KB first visit). 104 of 107 resources are served from browser cache, saving 4.07g CO2 per repeat visit.
Info::
Repeat visit: 0.01g CO2 (first visit: 4.08g)
First visit
17650 KB
Repeat visit
26 KB

100% reduction on repeat visits

Saving 4.07g CO2 per returning visitor

104 resources served from cache · 3 resources re-downloaded

A+
Transfer Efficiency
97% efficient
PASS
97% efficient
Info::
Transfer efficiency: 97%
Only 529 KB of potential savings identified. Your page is well-optimized for size.
97% efficient

Total waste: 529 KB (3% of page weight)

Unused JS 529 KB

0.12g unnecessary CO2 per visit

Actual transfer 17650 KB
Theoretical minimum 17121 KB
Potential savings 529 KB (0.12g CO2)

See Deep Analysis sections above for specific optimizations.

A+
Green Hosting
Whether the site is served from green-energy infrastructure
PASS

Green Hosting

This site is hosted on green energy infrastructure

Provider: Cloudflare

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

Send Feedback