Skip to content
https://martinfowler.com

Sustainability

· 6 checks — CO2 emissions, green hosting, repeat-visit weight, carbon budget, and transfer efficiency rolled into one auditable list.
SCORE
76
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
Not green
FIX
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 Apache HTTP Server✗CDN Not identified✗

Based on known provider commitments. Verify at thegreenwebfoundation.org

B
CO2 Per Page Load
0.53g CO2 per view
REVIEW
0.53g CO2 per view
Info::
0.53g CO2 per page view
This page transfers 1.9 MB, producing an estimated 0.53g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.10g, network 0.09g, end-user device 0.34g.
Got: 0.53g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 64.0 kg CO2/year
With 10,000 page views per month, this page would generate approximately 64.0 kg of CO2 annually — equivalent to charging 8005 smartphones.

0.53g

Carbon Footprint per page view

✗ Above sustainability target (0.50g)

Cleaner than 57% of websites

Sustainable Web Design model v4 · Page size: 1.9 MB

Your site
0.53g
Top 10%
0.20g
Target
0.50g
Median website
0.60g

Energy Breakdown

Data center
0.10g
Network
0.09g
End-user device
0.34g
At 10,000 monthly views: Monthly: 5.3 kg · Annual: 64.0 kg · ≈ 8005 smartphone charges
B
Carbon Budget
43th percentile
REVIEW
43th percentile
Info::
0.53g CO2 — below the median website (0.60g)
Better than an estimated 57% of websites, but above the sustainability target of 0.50g. Reducing page weight would help reach the target.
Info::
Estimated 43th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website

0.53g

43rd percentile

Cleaner than 57% of websites

✗ Above the median website

vs Median 11% cleaner ✓
vs Target 7% more
C
Green Hosting
Action
Whether the site is served from green-energy infrastructure
REVIEW

Green Hosting

No green hosting detected

A+
Repeat Visit Weight
99% cached
PASS
99% cached
Info::
99% reduction on repeat visits
Returning visitors download only 10 KB (vs 1929 KB first visit). 24 of 25 resources are served from browser cache, saving 0.53g CO2 per repeat visit.
Info::
Repeat visit: 0.00g CO2 (first visit: 0.53g)
First visit
1929 KB
Repeat visit
10 KB

99% reduction on repeat visits

Saving 0.53g CO2 per returning visitor

24 resources served from cache · 1 resources re-downloaded

A+
Transfer Efficiency
99% efficient
PASS
99% efficient
Info::
Transfer efficiency: 99%
Only 20 KB of potential savings identified. Your page is well-optimized for size.
99% efficient

Total waste: 20 KB (1% of page weight)

Unused JS 20 KB

0.01g unnecessary CO2 per visit

Actual transfer 1929 KB
Theoretical minimum 1909 KB
Potential savings 20 KB (0.01g CO2)

See Deep Analysis sections above for specific optimizations.

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

Send Feedback