Skip to content
https://getbootstrap.com

Sustainability

· 6 checks — CO2 emissions, green hosting, repeat-visit weight, carbon budget, and transfer efficiency rolled into one auditable list.
SCORE
100
GRADE
A+
FIX
0
REVIEW
1
PASS
5
INFO
0
Device:
Mobile Desktop
Checks
6
5 PASS 1 REVIEW
B
Transfer Efficiency
88% efficient
REVIEW
88% efficient
Info::
Transfer efficiency: 88%
An estimated 31 KB (12%) could be eliminated: 0 KB via better compression, 0 KB via modern image formats, 31 KB of unused JavaScript. This wasted data produces 0.01g of unnecessary CO2 per page view.
88% efficient

Total waste: 31 KB (12% of page weight)

Unused JS 31 KB

0.01g unnecessary CO2 per visit

Actual transfer 256 KB
Theoretical minimum 225 KB
Potential savings 31 KB (0.01g CO2)

See Deep Analysis sections above for specific optimizations.

A+
CO2 Per Page Load
0.06g CO2 per view
PASS
0.06g CO2 per view
Info::
0.06g CO2 per page view
This page transfers 0.3 MB, producing an estimated 0.06g of CO2 per visit using the Sustainable Web Design model (v4). Breakdown: data center 0.00g, network 0.01g, end-user device 0.05g.
Got: 0.06g CO2 Expected: < 0.50g (sustainability target)
Info::
At 10,000 monthly views: 7.1 kg CO2/year
With 10,000 page views per month, this page would generate approximately 7.1 kg of CO2 annually — equivalent to charging 889 smartphones.
Info::
Green hosting reduces data center emissions

0.06g

Carbon Footprint per page view

✓ Below sustainability target (0.50g)

Cleaner than 90% of websites

Sustainable Web Design model v4 · Page size: 0.3 MB

Your site
0.06g
Top 10%
0.20g
Target
0.50g
Median website
0.60g

Energy Breakdown

Data center
0.00g
Network
0.01g
End-user device
0.05g
At 10,000 monthly views: Monthly: 0.6 kg · Annual: 7.1 kg · ≈ 889 smartphone charges
A+
Green Hosting
Green (both)
PASS
Green (both)
Info::
Both hosting and CDN use renewable energy
Got: Hosting: GitHub Pages, CDN: Cloudflare
Info::
GitHub Pages: 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 GitHub Pages✓CDN Cloudflare✓

GitHub Pages: 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
93% cached
PASS
93% cached
Info::
93% reduction on repeat visits
Returning visitors download only 17 KB (vs 256 KB first visit). 21 of 22 resources are served from browser cache, saving 0.06g CO2 per repeat visit.
Info::
Repeat visit: 0.00g CO2 (first visit: 0.06g)
First visit
256 KB
Repeat visit
17 KB

93% reduction on repeat visits

Saving 0.06g CO2 per returning visitor

21 resources served from cache · 1 resources re-downloaded

A+
Carbon Budget
10th percentile
PASS
10th percentile
Info::
0.06g 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

0.06g

10th percentile

Cleaner than 90% of websites

✓ Below the Web Sustainability Guidelines target

vs Median 90% cleaner ✓
vs Target 88% 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: Cloudflare

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

Send Feedback