Skip to content
https://mozdev.org

Sustainability

· 6 checks — CO2 emissions, green hosting, repeat-visit weight, carbon budget, and transfer efficiency rolled into one auditable list.
SCORE
88
GRADE
B
FIX
0
REVIEW
2
PASS
4
INFO
0
Device:
Mobile Desktop
Checks
6
4 PASS 2 REVIEW
B
Green Hosting
Green (hosting)
REVIEW
Green (hosting)
Info::
Google Cloud uses renewable energy
Info::
Google Cloud: Verified by the Green Web Foundation
Info::
Google Cloud CDN: Inherits Google Cloud regional renewable mix
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 Google Cloud✓CDN Google Cloud CDN✗

Google Cloud: Verified by the Green Web Foundation

Google Cloud CDN: Inherits Google Cloud regional renewable mix

Based on known provider commitments. Verify at thegreenwebfoundation.org

C
Transfer Efficiency
Action
74% efficient
REVIEW
74% efficient
Warning::
Transfer efficiency: 74%
An estimated 202 KB (26%) could be eliminated: 0 KB via better compression, 0 KB via modern image formats, 202 KB of unused JavaScript. This wasted data produces 0.05g of unnecessary CO2 per page view.
74% efficient

Total waste: 202 KB (26% of page weight)

Unused JS 202 KB

0.05g unnecessary CO2 per visit

Actual transfer 774 KB
Theoretical minimum 571 KB
Potential savings 202 KB (0.05g CO2)

See Deep Analysis sections above for specific optimizations.

A+
CO2 Per Page Load
0.18g CO2 per view
PASS
0.18g CO2 per view
Info::
0.18g CO2 per page view
This page transfers 0.8 MB, producing an estimated 0.18g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.00g, network 0.04g, end-user device 0.14g.
Got: 0.18g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 21.5 kg CO2/year
With 10,000 page views per month, this page would generate approximately 21.5 kg of CO2 annually — equivalent to charging 2683 smartphones.
Info::
Green hosting reduces data center emissions

0.18g

Carbon Footprint per page view

✓ Below sustainability target (0.50g)

Cleaner than 90% of websites

Sustainable Web Design model v4 · Page size: 0.8 MB

Your site
0.18g
Top 10%
0.20g
Target
0.50g
Median website
0.60g

Energy Breakdown

Data center
0.00g
Network
0.04g
End-user device
0.14g
At 10,000 monthly views: Monthly: 1.8 kg · Annual: 21.5 kg · ≈ 2683 smartphone charges
A+
Repeat Visit Weight
97% cached
PASS
97% cached
Info::
97% reduction on repeat visits
Returning visitors download only 21 KB (vs 774 KB first visit). 52 of 53 resources are served from browser cache, saving 0.17g CO2 per repeat visit.
Info::
Repeat visit: 0.00g CO2 (first visit: 0.18g)
First visit
774 KB
Repeat visit
21 KB

97% reduction on repeat visits

Saving 0.17g CO2 per returning visitor

52 resources served from cache · 1 resources re-downloaded

A+
Carbon Budget
10th percentile
PASS
10th percentile
Info::
0.18g CO2 — below the sustainability target of 0.50g
Cleaner than an estimated 90% of websites analyzed. This page meets the Web Sustainability Guidelines target.
Info::
Estimated 10th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website

0.18g

10th percentile

Cleaner than 90% of websites

✓ Below the Web Sustainability Guidelines target

vs Median 70% cleaner ✓
vs Target 64% cleaner ✓
A+
Green Hosting
Whether the site is served from green-energy infrastructure
PASS

Green Hosting

This site is hosted on green energy infrastructure

Provider: Google Cloud

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

Send Feedback