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https://kayak.com

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
1.49g CO2 per view
FIX
1.49g CO2 per view
Warning::
1.49g CO2 per page view
This page transfers 6.3 MB, producing an estimated 1.49g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.04g, network 0.31g, end-user device 1.14g.
Got: 1.49g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 178.4 kg CO2/year
With 10,000 page views per month, this page would generate approximately 178.4 kg of CO2 annually — equivalent to charging 22293 smartphones.
Info::
Green hosting reduces data center emissions

1.49g

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
1.49g
Top 10%
0.20g
Target
0.50g
Median website
0.60g

Energy Breakdown

Data center
0.04g
Network
0.31g
End-user device
1.14g
At 10,000 monthly views: Monthly: 14.9 kg · Annual: 178.4 kg · ≈ 22293 smartphone charges
F
Carbon Budget
Action
75th percentile
FIX
75th percentile
Warning::
1.49g 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

1.49g

75th percentile

Cleaner than 25% of websites

✗ Above the median website

vs Median 148% more
vs Target 197% more
B
Transfer Efficiency
79% efficient
REVIEW
79% efficient
Info::
Transfer efficiency: 79%
An estimated 1354 KB (21%) could be eliminated: 0 KB via better compression, 0 KB via modern image formats, 1354 KB of unused JavaScript. This wasted data produces 0.31g of unnecessary CO2 per page view.
79% efficient

Total waste: 1354 KB (21% of page weight)

Unused JS 1354 KB

0.31g unnecessary CO2 per visit

Actual transfer 6430 KB
Theoretical minimum 5075 KB
Potential savings 1354 KB (0.31g 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::
Fastly CDN uses renewable energy
Since most traffic is served through the CDN, the majority of data transfer energy is renewable.
Info::
Fastly: 100% renewable energy for edge network
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 Not identified✗CDN Fastly✓

Fastly: 100% renewable energy for edge network

Based on known provider commitments. Verify at thegreenwebfoundation.org

A+
Repeat Visit Weight
96% cached
PASS
96% cached
Info::
96% reduction on repeat visits
Returning visitors download only 244 KB (vs 6430 KB first visit). 599 of 606 resources are served from browser cache, saving 1.43g CO2 per repeat visit.
Info::
Repeat visit: 0.06g CO2 (first visit: 1.49g)
First visit
6430 KB
Repeat visit
244 KB

96% reduction on repeat visits

Saving 1.43g CO2 per returning visitor

599 resources served from cache · 7 resources re-downloaded

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

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