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Reduce the carbon emissions of your website

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  • hannah 
Reduce carbon emissions

Through this action, we encourage you to assess and reduce the carbon emissions of your website as well as share your approach with others.

Below you will find information to guide you on the most positive and effective way to do this including:

Why this action matters

Many people don’t know that every time a website is loaded, it is responsible for carbon emissions. In fact, estimates suggest that if the internet were a country, it would be the world’s seventh-biggest polluter. Even if we can’t easily see the footprint that cyberspace leaves on our physical environment, the impact is certainly real.

Reducing the carbon emissions associated with a website boils down to reducing the amount of electricity being used to load, send, and view a web page, and then ensuring the resulting electricity required is from clean, renewable resources. 

The great thing about making a website more carbon friendly is that it often brings out additional benefits such as:

  • Making the website cheaper to run
  • Improving load times and performance
  • Providing a better content experience for users

By taking this action you are playing an important part in reducing the carbon emissions arising from the tech sector.

How you can take part

  1. Estimate the carbon emissions of your website. The Website Carbon Calculator is a great tool if you are new to the subject. If you are looking for something more in depth check out our Resources section below.
  2. Review the estimate and identify ways you can change your site. Our resources below recommend good starting points for things you can easily change.
  3. Make changes to your code, content, or internal processes.
  4. Re-estimate your carbon emissions. Find out what impact your changes have made.
  5. Share with us what you have done. Post in the comments section at the end of this post.

Resources to help you 

Tools for measuring carbon emissions and the impact of your website

Leaderboards for tracking the impact of the world’s largest company websites

Our recommended starting points for making your site greener

Remove and restructure

Delete things that are not essential and make the rest leaner

Review media

Images & videos usually contribute the most to your page file size

Move to a green host

Reduce your site’s carbon emissions by approx 10%

Cache things

Implement database and browser caching

Further articles and insight on practical steps you can take

Introductory articles

Introductory video

Resources that will take you a little deeper



Find out more about other communities in our Join a Community action guide.

Frequently asked questions

What are the best technologies to consider for building a sustainable website?

There’s no direct correlation between a web technology and the sustainability of the websites or web-apps that are built with it. Your carbon emissions estimate will mostly depend on an efficient implementation of the technology, and the correct implementation of web standards, web caching techniques and browser capabilities.

At the end of this page you will find case studies and stories relating to all sorts of web technologies being used to create websites with low carbon emissions.

Do you have to be a developer to reduce the carbon emissions of a website?

No, there are lots of ways we can reduce the carbon emissions of a website other than through code. Graphic design, UX, and content choices affect the emissions from a site, so anyone involved in creating a website has a role to play. 

Consumers have an important role to play as well. Raising demand for certain services or changes has a powerful impact on companies, and everyone’s voice matters in helping to catalyze action. Take a look at our Action Guide titled Share the carbon impact of your favorite company’s website for how you can help raise awareness about the carbon emissions that websites create.

If I estimate a website’s CO2 emissions using different tools, I get different numbers. Why is that?

Estimating carbon emissions for websites is a really difficult thing to do as there are so many variables to consider.

Things that can vary dramatically for each user include: the distance the user is from the site’s server, what device the site is viewed on (mobile, laptop, TV), whether the data is being received by wifi or a cabled connection, what sort of energy mix is the server running on etc etc. All these things will affect the estimate.

So any tool that offers a calculation has to make some assumptions about these things, and many other varying factors not listed here.

On top of that the numbers that you would use for the calculations, once the assumtions are made, keep changing as well!  For example, the carbon intensity of producing energy in each country changes each year, and the efficiency of transferring data from one place to another also typically rises each year. A calculation using the best data one month will be out of date by the next month, because things shift within the digital world so quickly.

Our advice, is that any tool that offers you a carbon emissions estimate for a website should be taken as an estimate, not as fact. Use these estimates as a guide to let you know roughly how well a site is doing.

Will my effort matter next to the impact of giants such as Youtube?

Yes! While the big tech giants undoubtedly have a significant responsibility to make their infrastructure sustainable, it’s important to consider two things. 

1. In some ways, having such large operations – and the resources and purchasing power that comes with it – makes it easier to scale more sustainable technologies assuming there is the sheer will to do so. 

2. More importantly, even small websites can have a meaningful carbon output over time. As you can see from this analysis of the USA Today news website by Chris Adams, one of the organisers of ClimateAction.Tech. He calculated that, given the daily traffic their website experienced at the time, it produced just under a quarter of a tonne of CO2 per day, which is “comparable to something like taking a short-haul flight from New York to Chicago”. Even if a website gets far fewer hits per day, it’s important to remember that there are approximately more than 1.5 billion websites on the Internet. This all adds up over time, especially if you also consider things like the energy required to transfer data from a server to your device, often over long distances.

Does my website still have an impact if it runs on renewable energy?

Yes. Although choosing a hosting company that runs on renewable energy may be one of the biggest actions you can take, you also need to optimise your content: both how it is loaded and what it is. Keep in mind that storing and accessing large and inefficient websites takes more resources. Electricity is not the only resource you require either; it is also the server and the hard drive to store your site‘s data. All these physical devices need to be manufactured, maintained, and replaced.

And, unfortunately, fossil fuels are still often required to produce (the equipment that generates) renewable energy.

Is this still an issue if I cache my pages efficiently?

Caching is a good help, but not the only thing you can do. Caching is what we all should do, for all websites where possible. It is part of the optimisation of the performance of a website at the end of the development process

But real optimisation of a web project should start at the beginning with critical assessment of design elements, like images. Do we really need that large (stock) photo, do we really need a bloated framework, etc.

Moreover, browser caching only works on the second and adjacent page loads. The largest impact on the visitor is the first visit: that is where you make the first impression.

How do I sell a carbon friendly website to my client as a web designer/developer?

The benefits of a carbon-friendly website align with that of a fast, efficient, and user-friendly website, powered by a server on sustainable energy. So help your client understand that they can have a fast, performant website and an eco-friendly one at the same time.

Beyond the immediate performance gains, sustainability is increasingly cited as a priority among both businesses and consumers. After all, going green isn’t just good for the planet; many understand that it also benefits the bottom line.

Why sustainability is the new digital is an interesting read on this topic. It draws parallels between the concept that ‘every business is a digital business‘ which came about in the early 2000s, and a new emerging concept that the business of sustainability has come of age e.g. ‘every business is a sustainable business‘. A review of 100 studies crushes assumptions about conflict between profit and sustainability, published by Anthropocene Magazine, further supports the notion that sustainability is good for business. For a more tech focused read, check out To Green the Internet, We Need RIPE.

Is there a recommended place to find a developer to help me reduce the carbon emissions of my website?

Here are a few directories that list people who may be able to help you:

The Sustainable Dev directory
Climate Base People profiles

Case studies and stories

Directories – a showcase of websites that prove you can have a well-designed, accessible internet presence, but with a low carbon impact on the planet – browse through lightweight, user-friendly, aesthetic and sustainable UX/UI designs of the web – this directory of lightweight websites has been created to inspire actors of the digital industry to design and build lighter and greener products.

Here’s a collection of posts that others have written about their experiences of reducing or analysing the carbon emissions of a website. If you have a suggestion for a post you would like to see included in this section, you can tell us in the comments section.







  • Hannah Smith
  • Michael J. Oghia
  • Stefanie Mühlbacher
  • Csaba Varszegi

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What others are saying

  1. As someone working as an SEO specialist, I’m trying to see how I can get other SEOs involved in this as I think its a really important one. Ironically as SEOs our main job results in amplifying the carbon emissions of websites through increasing traffic to our client’s websites, so I think we have an important part to play in trying to reduce carbon emissions of those sites.
    If anyone reading this wants to help or get involved with what I’m trying to do, feel free to reach out!

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