How to measure the carbon footprint of a web page

For the most of us it comes as a surprise: our digital activities have a carbon footprint. It is significant and growing rapidly, especially during a pandemic where we are obliged to communicate much more through the internet. It comes from different sources, but it is hard to measure what the actual footprint is. Fortunately, we have tools to measure the carbon footprint of websites.

Website carbon tool

Website carbon

Website carbon is a great tool to estimate the carbon footprint of a web page. It has kindly been created by Wholegrain Digital, a sustainable web design agency from London, UK. The tool is meant ‘to help inspire and educate people to create a zero carbon internet’.

The tool tells you two things:

  1. The carbon footprint of the web page as CO2 equivalent. At the time of writing, the average web page tested produces 0.5 g CO2 per page view. For a website with 10,000 monthly page views, that’s 211 kg CO2 per year.
  2. Whether your website is hosted on renewable energy.

The average web page tested produces 0.5 g CO2 per page view.

The amount of CO2 produced by loading your page is compared to a couple of fun things, like the amount of bubbles in a soda, but also to the amount of CO2 absorbed by trees and the distance you can drive with an electric car with the amount of energy.

Below the results, clear actions encourage you to reduce the footprint.

The homepage of Global Warning generates about 0.02 g CO2 per page load. This is cleaner than 97% of the web pages tested. Over a year, with 1100 page views a month, it would equal to 550 Wh, which is enough electricity to drive an electric car 3.3 km.

They have also a badge available that you can easily add to your web page. I encourage you to do it because:

  • It has only a minimal impact on your page load.
  • It will educate people about the carbon footprint of the web.
  • It can endorse your website as being environmentally conscious.
  • It generates useful data for the tool to enable tracking the evolution of carbon footprints.

Digital Beacon

I found another tool I was not familiar with, it is called (Digital) Beacon. This tool (still in beta) is created by Generate Space, a company providing sustainable solutions with strong aesthetics.

The tool is using the Website carbon tool behind the scene. The estimate it generates is therefore the same, but the results are displayed in more technical detail. The results give more insight in which assets contribute to the footprint and gives an overview of opportunities, based on web vitals and more. The tool seems to be aiming more at web professionals.

Digital Beacon gives each page a rating between ‘amazing’ and ‘bad’. The homepage of Global Warning gets the highest ranking of ‘amazing’ for less than 0.25 g CO2 emission. ‘Bad’ is for web pages generating more than 1.5 g CO2. And unfortunately, this is the case for the average web page as tested by the Website Carbon tool!

So websites have a carbon emission, then what?

It is complicated to estimate carbon emissions as it is about more than just the web page size. The energy source used by the data center, the energy intensity of data (what it costs in terms of electricity to transfer and process data), the efficiency of the end-user’s device, the behaviour of the page after it is loaded, … must all be taken into consideration. It is also interesting to note that running on renewable energy (having a ‘green host’) does not magically make your site carbon neutral. Around 10% reduction in carbon emission is calculated when a site is hosted by a green host. Check the Green Web Foundation to find a green host near you. Keep in mind that these hosts may be (partly) offsetting their emission, so not running (completely) on renewable energy!

Overall, carbon emission estimates give you an idea about the environmental impact of visiting a web page or loading your own website, and the internet in general. They also point out differences between websites or pages.

Just do it

So it is probably time to improve the web and your website in particular. There is a lot you can do. You can start with this overview at If you want to dive deeper, you can read Tom Greenwood’s book about Sustainable Web Design.

The internet will be the basis of a lot of great services of the future, let’s build it the right way! #LetsGreenTheWeb

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