Website Impact Optimisation

About

Website Impact Optimisation gives you an instant carbon footprint and performance optimisation audit of any webpage you visit — right from your browser toolbar.

The environmental impact of the web is real. Every page load consumes energy, produces CO₂ emissions, and contributes to the climate impact of digital infrastructure. WIO makes that invisible cost visible — and actionable.

Built on the open SWDM v4 (Sustainable Web Design Model) methodology and verified hosting data from the Green Web Foundation, every scan is grounded in recognised industry standards for measuring carbon emissions online, not guesswork.

What it does
Click the extension on any page and within seconds you'll see:
An A+ to F impact rating — a single, clear grade based on the CO₂ emissions produced every time the page loads, with a visual position on the full rating scale.
Green hosting check — instantly flags whether the site is running on renewable, clean energy or fossil-fuel servers, using live data from the Green Web Foundation. Switching to green hosting cuts a site's carbon emissions by up to 85%.
Per-page load metrics — page weight, Time to First Byte (TTFB), a composite tech health and efficiency score out of 100, and precise CO₂e per load in grams.
Global ranking — see how this page's carbon footprint compares to other websites in your region (UK, US, EU, or global), expressed as a clean percentile.
Annual impact calculator — set your monthly page view count and instantly see the full yearly CO₂ emissions expressed in six human-scale equivalents: cups of coffee brewed, miles flown economy class, miles driven in a petrol car, phone charges, hours of Netflix streaming, and how long it takes a tree to absorb the equivalent carbon.
Technical audit — a scored breakdown of seven performance, efficiency, and sustainability factors: page weight, image formats (WebP/AVIF), lazy loading, third-party scripts, render-blocking resources, caching headers, and dark mode support. Each metric scored 0–100 with pass / warn / fail status. A lower score across these factors means greater energy use per visit.
Optimisation tips — actionable, specific advice for reducing emissions and improving performance based on what the audit actually found. No generic suggestions — only tips relevant to the ecological and efficiency issues on this page.
PDF export — one-click export of a clean, print-ready sustainability report covering the impact rating, annual carbon equivalents, and full audit table. Useful for sharing with clients or development teams working toward net zero digital goals.
Dark mode — full light and dark theme, remembered between sessions. Dark mode support is itself an energy efficiency win on OLED screens — WIO audits for it too.

How it works
WIO uses your browser's native Performance API to measure real resource data — the actual bytes transferred for every asset the page loaded. No third-party services, no proxies, no external scanning. All carbon emissions calculations run locally in your browser.
The only external call is a single hostname check against the Green Web Foundation API to verify whether the hosting is powered by renewable, clean energy. No full URLs are ever sent.

Privacy first

No browsing history stored
No URLs logged or tracked
No analytics or telemetry
Session data (pages scanned, total CO₂ grams) lives in memory only and is cleared when you close the popup
Green Web Foundation check sends the hostname only — never the full URL

Carbon methodology
Carbon footprint calculations use SWDM v4 — the Sustainable Web Design Model published by Wholegrain Digital and the Sustainable Web Design community. This is the same open methodology used by leading sustainability and decarbonisation tools across the industry.
Constants used:

0.81 kWh per GB of data transfer (energy use factor)
494 gCO₂e/kWh global average grid intensity
85% carbon emissions reduction factor for verified renewable green hosting

Rating thresholds follow the recognised scale across the sustainable web community, from A+ (under 0.095g CO₂e per load) to F (1g or above) — making it easy to benchmark a site's ecological footprint against global standards.

Who is it for?
Web developers running performance optimisation and wanting to understand the carbon footprint of their builds
Designers making eco-conscious decisions about assets, fonts, and third-party scripts
Agencies and studios producing sustainability reports and advising clients on net zero digital strategy
Site owners wanting to understand the environmental impact and energy use of their web presence
Anyone curious about the CO₂ emissions, climate impact, and ecological cost of the web

Built by Forest Web Hosting
Forest Web Hosting is a UK-based green web host committed to sustainable, renewable, clean digital infrastructure. WIO was built to make carbon footprint awareness and performance optimisation accessible to everyone — because decarbonisation of the web starts with understanding the emissions it produces.
theforest.uk