With an increased focus on the climate and our planet’s future, sustainability is a concern across all areas of our lives. 

And that applies to websites now too. Chris Baker, Director of a leading London web design agency, explains, “We recently created a site for the COP26 conference where sustainability was a deciding factor for the client. As such, creating websites that are sustainable and reduce an organisation’s carbon footprint is expected to become standard practice with less data-intensive design elements taking centre stage.” 

So, how can you create a sustainable website? What does that really mean? We’re breaking it down in this short read.

What does website sustainability mean?

According to the leading organisation behind this movement, “Sustainable web design is an approach to designing web services that puts people [and the planet] first. It delivers digital products and services that respect the principles of the Sustainable Web Manifesto: clean, efficient, open, honest, regenerative, and resilient.” It looks to minimise the computing power needed to operate a website and focuses on using clean energy sources when it does. By looking at data transfer stats, web traffic, energy use and more, websites are evaluated and scored for their efficiency.

Website carbon scores

Tools like this one can provide you with a snapshot of how well your website is performing versus other web pages in terms of environmental friendliness. It tells you how much CO2 is created per visit and if the site is powered by sustainable resources.

And it can calculate the annual environmental impact of the website as a result. This allows even green sites to offset their carbon emissions via tree-planting or financial contributions if they wish.

How is a website’s carbon footprint determined?

This carbon footprint score is calculated based on a number of factors that might vary based on the calculator you use.  But generally, these include:

Data transfer over the wire

This looks at how much data is transmitted when the website loads and its relation to total energy usage. It also accounts for visitors who may have some elements saved to their cache and therefore need less data to load the pages. When combined with the other metrics, this contributes to overall energy use and CO2 impact score.

Energy intensity of web data

This figure is the average for a given location. In the UK, this might be 1.8kWh/GB. And that’s based on all the extra energy used to access the web from your device to your ISP. While this varies, using this average is helpful as a baseline for the other calculations involved in determining website sustainability.

The energy source used by the data centre

man working in front of his laptop

According to Website Carbon, “To gauge the energy source, we assume that all websites use standard grid electricity for the telecoms network and [end-user] since we have no way to determine otherwise.  For the data centre energy use, we check the Green Web Foundation (GWF) database to see if the data centre is using green energy.  If so, then we reduce the carbon emissions attributed to that portion of the energy accordingly. We estimate the proportion of energy used in the data centres to be approximately 10% by comparing the global data centre energy usage stated in the Nature article to total ICT energy usage (excluding manufacturing) in the Andrae and Edler report.”

Carbon intensity of electricity

Once the amount of energy used is determined, that energy is assigned a carbon value. For the grid, that might be 475 grams CO2e per kWh and for renewable sources, that average could be set at 33.4 grams CO2e per kWh.

Website traffic

With all the above, you only need to know the annual website traffic stats for that page to come up with a carbon score.

How can you reduce your website’s carbon footprint?

Once you know how well (or poorly) your website is scoring, you can take steps to improve your impact. Some popular ways to do so is:

Less video

Video uses a lot of energy to load. By reducing the amount of video you use on your website, you’re decreasing your environmental impact. If you must use video, don’t allow it to auto-play. By requiring user intent before playing any video asset, you’re preventing unnecessary data transfer and conserving what energy you can.

Image compression

Lazy loading and image compression can help reduce the amount of data required to load a website. According to the CMI, “images made up on average 21% of a total web page’s weight as of November 2018. Because images consume more bytes than any other part of a website, their size and complexity heavily influence site performance. If you reduce the size of images without compromising quality, page load times improve and, subsequently, the experience of website visitors does too.” So improved conversions and better SEO follow on from image optimisation.

Data stored and accessed via sustainable energy sources

Next, consider where you store your data and host your website. Look for data centres located in countries with the highest percentage of their energy from renewable sources. So, based on this data, you’d have a more sustainable website if you moved your hosting & storage from Australia to the Netherlands, for example.

Fast loading

Overall, across your entire digital estate, you want to focus on fast loading. Not only will this help your SEO, but it will reduce your carbon footprint. Eliminate clunky downloadables, large infographics, cluttered animation, iframes and more to trim the data loads down to the bare minimum. 


Looking after the environmental impact of our digital footprint is becoming more important than ever. As a connected society, a lot of harm can be averted by taking our data usage into account. Moving to more eco-friendly data centres, streamlining our content, incorporating user choice into data transfer and compressing our images can go a long way to reducing our carbon emissions. Once you’ve made these changes, count on the green economy to reward your business for leading on the sustainable website design front.

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