WHAT IS A WEBSITE CARBON FOOTPRINT?
Your website produces CO₂ every time someone visits it. Here's what that means, how it's calculated, and what you can do about it.
Test Your Website's Carbon Footprint →The Definition
A website carbon footprint is the total amount of CO₂-equivalent greenhouse gases emitted as a direct result of loading a webpage. It covers emissions from the data centers that host the files, the networks that transmit the data, and the devices that render it for the user.
Unlike a company's operational carbon footprint (buildings, travel, manufacturing), a website's carbon footprint is entirely digital — and therefore entirely within the control of developers, designers, and product teams.
How Website CO₂ Emissions Are Calculated
The industry standard for estimating website emissions is the Sustainable Web Design (SWD) model, developed by Wholegrain Digital and the Green Web Foundation. The formula is:
MyCarbonScan uses Puppeteer to load pages in a real browser and intercepts every network request via the Chrome DevTools Protocol. This gives us the true encodedDataLength of every resource — HTML, CSS, JavaScript, images, fonts, analytics, and third-party scripts — for an accurate byte count. That byte count is then fed into the SWD model to produce the final CO₂ figure.
Website Carbon Benchmarks
Where does your site sit relative to the rest of the web?
Top 10% of websites
< 0.09g CO₂ per page view
Average website
~0.5g CO₂ per page view
Heavy websites (video, animations)
> 1.0g CO₂ per page view
Simple text/blog page
0.03g – 0.15g CO₂ per page view
To put these figures in context: a site with 50,000 monthly page views and an average of 0.5g CO₂ per view produces 25 kg of CO₂ per month — equivalent to driving roughly 100 miles in a petrol car.
Why Your Website's Carbon Footprint Matters
Environmental impact
The internet accounts for 2–4% of global carbon emissions. Digital technology is projected to grow to 14% of global emissions by 2040 if left unchecked.
EU regulatory pressure
The EU Corporate Sustainability Reporting Directive (CSRD) requires large companies to report Scope 3 emissions — which include digital infrastructure. US companies with EU customers or subsidiaries are already in scope.
Brand and client trust
B2B buyers and enterprise procurement teams increasingly ask for sustainability data. A measurable, publicly reported website carbon score is a credible signal.
Performance correlation
A lower-carbon website is almost always a faster website. The same optimizations that cut data transfer — compressed images, trimmed JavaScript, deferred third-party scripts — also improve Core Web Vitals and SEO.
How to Measure Your Website's Carbon Footprint
One-off tests (like the free Website Carbon Calculator from Wholegrain Digital) give you a snapshot, but they don't track changes over time — which means you can't tell if an optimization actually reduced emissions, or if a new page version made things worse.
MyCarbonScan gives you ongoing monitoring: add your URLs, and the tool automatically rescans them every day. You get trend charts, historical data, A–D sustainability ratings, and CSV/PDF export for stakeholder reporting. Up to 100 URLs on one plan — $299/month with a 14-day free trial.
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Measure Your Website's Carbon Footprint
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