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Sustainability

Sustainability is the future.
Are you sustainable?

Consumption and emissions belong together – just like cause and effect. If consumption goes up, the footprint gets bigger. If awareness goes up, action will follow. Expectations are evolving. So we raise awareness.

The way we test

Websites come to life in the user's browser – not on the server. The server only delivers the building blocks. How a page actually looks, behaves and performs is determined in the browser. Anyone testing only on the server is checking the plan, not the result. Whether a page truly works becomes visible on the screen where it appears. That's where we look.

A heavy website costs

The average web page has grown 100× heavier in 20 years. Every unnecessary kilobyte costs conversion rates, Core Web Vitals scores, hosting bandwidth, and CO₂ emissions. Sustainability and performance are the same problem.

Unoptimized images (no WebP, oversized)High — LCP, bandwidth
No HTTP compressionHigh — 60-80% transfer overhead
Excessive third-party scriptsHigh — blocking, carbon, privacy
Missing browser caching headersMedium
Non-lazy-loaded off-screen imagesMedium — FCP, bandwidth
Render-blocking JS/CSSHigh — TTI
Green hosting unverifiedMedium — ESG reporting
Excessive total requestsMedium

12 sustainability checks in 4 areas

Automated checks that catch the performance and efficiency issues driving unnecessary carbon emissions.

Page Weight & Transfer Size

Total page weight (HTML + CSS + JS + images + fonts)
Industry benchmark comparison (< 500KB recommended)
Transfer size vs. raw size ratio (compression effectiveness)
Largest assets identified by type

Asset Optimization

Image format: WebP/AVIF used vs. legacy JPEG/PNG
Image dimensions: served at display size?
Image lazy loading: off-screen images deferred?
Total image payload
Font loading: system fonts vs. web font weight

Delivery Efficiency

HTTP compression: gzip or Brotli active?
HTTP/2 or HTTP/3: multiplexed connections?
Total request count
Cache headers: browser caching configured?
CDN detected?

Carbon & Hosting

Green hosting: verified against The Green Web Foundation database
Estimated CO₂ per visit based on transfer size and energy mix
Benchmark comparison: equivalent carbon metrics

What we check

Sustainability

11 automated checks

Page Weight

Asset Optimization

Sustainability FAQ

Common questions about website carbon footprint and sustainability.

    Website Carbon Footprint & Sustainability Audit | RGate | RGate