https://preply.com
Sustainability
· 6 checks — CO2 emissions, green hosting, repeat-visit weight, carbon budget, and transfer efficiency rolled into one auditable list.SCORE
80
GRADE
B
FIX
0
REVIEW
3
PASS
3
INFO
0
Checks
63 PASS 3 REVIEW
BCO2 Per Page Load0.61g CO2 per viewREVIEW
CO2 Per Page Load
0.61g CO2 per view
0.61g CO2 per view
Info::
0.61g CO2 per page view
This page transfers 2.6 MB, producing an estimated 0.61g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.02g, network 0.13g, end-user device 0.47g.
Got: 0.61g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 73.2 kg CO2/year
With 10,000 page views per month, this page would generate approximately 73.2 kg of CO2 annually — equivalent to charging 9156 smartphones.
Info::
Green hosting reduces data center emissions
0.61g
Carbon Footprint per page view
✗ Above sustainability target (0.50g)
Cleaner than 50% of websites
Sustainable Web Design model v4 · Page size: 2.6 MB
Your site
0.61g
Top 10%
0.20g
Target
0.50g
Median website
0.60g
Energy Breakdown
Data center
0.02g
Network
0.13g
End-user device
0.47g
At 10,000 monthly views: Monthly: 6.1 kg · Annual: 73.2 kg · ≈ 9156 smartphone charges
BCarbon Budget50th percentileREVIEW
Carbon Budget
50th percentile
50th percentile
Warning::
0.61g CO2 — above the median website (0.60g)
Heavier than an estimated 50% of websites. Reducing page weight, optimizing images, and removing unused JavaScript would lower the carbon footprint. See the Performance tab.
Info::
Estimated 50th percentile
Compared to: top 10% = 0.20g, target = 0.50g, median = 0.60g per page view.
Top 10%
Target
Median website
0.61g
50th percentile
Cleaner than 50% of websites
✗ Above the median website
vs Median 2% more
vs Target 22% more
BTransfer Efficiency79% efficientREVIEW
Transfer Efficiency
79% efficient
79% efficient
Info::
Transfer efficiency: 79%
An estimated 552 KB (21%) could be eliminated: 0 KB via better compression, 0 KB via modern image formats, 552 KB of unused JavaScript. This wasted data produces 0.13g of unnecessary CO2 per page view.
Total waste: 552 KB (21% of page weight)
Unused JS 552 KB
0.13g unnecessary CO2 per visit
Actual transfer 2640 KB
Theoretical minimum 2088 KB
Potential savings 552 KB (0.13g CO2)
See Deep Analysis sections above for specific optimizations.
A+Green HostingGreen (both)PASS
Green Hosting
Green (both)
Green (both)
Info::
Both hosting and CDN use renewable energy
Got: Hosting: Agora, CDN: Cloudflare
Info::
Agora: 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 Agora✓CDN Cloudflare✓
Agora: 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 Weight94% cachedPASS
Repeat Visit Weight
94% cached
94% cached
Info::
94% reduction on repeat visits
Returning visitors download only 160 KB (vs 2640 KB first visit). 193 of 196 resources are served from browser cache, saving 0.57g CO2 per repeat visit.
Info::
Repeat visit: 0.04g CO2 (first visit: 0.61g)
First visit
2640 KB
Repeat visit
160 KB
94% reduction on repeat visits
Saving 0.57g CO2 per returning visitor
193 resources served from cache · 3 resources re-downloaded
A+Green HostingWhether the site is served from green-energy infrastructurePASS
Green Hosting
Whether the site is served from green-energy infrastructure
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.