How do websites impact global warming?

The internet generates a similar amount of CO2 in the environment as the global aviation industry. Your website most likely has an impact. This article explains how websites contribute to global warming, and how you can reduce your website carbon footprint.
24 Nov, 2021

Is my website contributing to global warming?

The simple answer is – yes!

The more complex answer would be that ‘yes, websites impact global warming’. Your website almost certainly does have an environmental impact. The extent of your website’s carbon footprint will be determined by a number of factors.

Your website runs on a web server. It might occupy the whole server (dedicated hosting), or, more likely, it will share the server with many other websites. This server is switched on 24 hours a day, 7 days per week, and so is consuming power just by existing.

The server will most likely be housed in a data centre. The data centre will need all the usual heating, lighting, and other power consumption capabilities required to support their employees and visitors, as well as the supercooling required to keep the servers at a safe and optimum operating temperature.

So, all of that… before you get any traffic!

Your traffic has a website carbon footprint too!

Your website consumes power just by existing on the server.

That’s a bit like leaving your computer switched on all day without doing anything.

When an internet user browses one of your pages, your server immediately pulls together all of the elements of the page (html, images, javascript, CSS files for styling your web page, and other files).

That’s a chunk of work to do, which, of course, consumes additional power – every time someone loads one of your pages. It’s not only real human visitors that load your website. Spammers, search bots, and other web crawlers also have an impact.

Your web server then needs to deliver these elements to your visitor’s browser so that it can display the page. This consumes power across the entire telecom network route between the server and your visitor’s computer. At DMJ, we refer to this as ‘web miles’.

Routers contribute to website carbon footprint

Every visitor to your website consumes power

Web Miles

Imagine the web miles that your content covers to get your page delivered to your visitor.

There’s a request that gets sent from your visitor’s computer (or phone or tablet) to their ISP. The ISP then devises the best route to get the message to the web server, passing through a number of intermediate locations, before it finally arrives (a fraction of a second later) at your web server. Your web server then gets all the elements together for that web page and sends them back down the line to your visitor’s computer.

Some website carbon footprint facts and figures

According to the website carbon calculator, an average web page view generates 1.76g of CO2.

Websites impact global warming less if hosted with DMJ Computer Services

Screenshot courtesy of – DMJ Computer Services 2021 result


How much CO2 does our website generate?

We tested our own website home page at, and it came out at a very credible 0.41g of carbon per visit. This puts us in the top 25% of the cleanest UK websites.

However, that’s not the whole story!

We only measured our home page. Other pages on our website might be lighter (or heavier). It takes no account of the total traffic we get in any period – so, busier sites with lower emissions may still emit more CO2 than less efficient sites that hardly get any traffic.


Average CO2 produced by a page view


Average CO2 per month (assumes 1,200 page views)

Average CO2 per website per year

How to make a website more environmentally friendly (some ‘possibly’ impractical suggestions)

There is always more that can be done to reduce your website’s carbon footprint. These improvements often require trade-offs for your business. For example:

  • You could deliver text-only web pages (think Wikipedia, but not as attractive). This is unlikely to appeal to your customers, who need a richer experience to persuade them to engage with you.
  • You could host your website in a hydroelectric-powered data centre, but then have to ship your content thousands of miles to your visitors, running up lots of web miles.
  • You could restrict access to your website to visitors from a single country. This doesn’t stop the request from coming into your server, but it would prevent content from going back the other way. Even if your business only has customers from one country, you still risk blocking genuine visitors whilst they are visiting another country, or if they are using a VPN. There is also a chance you will block search engine crawlers, which could impact your SEO.

Practical things you can do to make your website more environmentally friendly

Host your website in a green data centre

Not all website hosts are the same. Low cost usually means poor performance and poor support, but it might also point to a host that doesn’t invest in sustainability. Ask your web hosts how power efficient their data centre is. They should be able to tell you their Power Usage Effectiveness (PUE). A typical PUE for most data centres is 2.0, which means that for every 1kW of IT load, they use another 1kW for cooling, electrical losses, etc. A perfect PUE would be 1.0, and an inefficient data centre would have a PUE ratio of 3.0. Our data centre has a PUE of 1.2, for example, which is pretty high.

PUE shouldn’t be the only metric you look at when considering how energy efficient your data centre is. You might also want to consider Data Center infrastructure Efficiency (DCiE). explain it better than us when they say…

Unfortunately, that hasn’t stopped some people from publishing their PUE numbers in an attempt to market their facilities or design strategies. While their efforts to improve data center efficiency should be applauded, these metrics by themselves are not sufficient to determine data center efficiency. The conversation must include productivity. Are you getting the most out of your servers and storage? Are you maximizing processing power? Retiring idle servers? Consolidating and Virtualizing?


Host your website close to your main source of visitors

Make sure you also know where the data centre is located. If it is located thousands of miles away from the bulk of your visitors, this could result in a whole load of ‘web miles’ every time your website is visited. Hosting in the UK is generally the best idea if that’s where most of your website visitors reside.

Consider using a CDN (Content Delivery Network)

This is not an obvious one. CDNs are used to distribute your website content to other servers around the world. When someone visits your website, a CDN will deliver the content from the closest server.

This not only speeds up load times for those visitors further away from your origin server, but can cut down the number of web miles your content travels. The content will still need to be moved from your origin server to the CDN server(s) once and will be updated from time to time as your content changes. If you have a lot of website traffic from visitors who are located a long way from your web server, this can really save CO2.

Keep your website and server software up-to-date

Platforms like WordPress use the PHP programming language, as well as other software to enable the web server to function. Over time, code within these software products will evolve to make them run quicker and more efficiently. This can have an impact on power consumption and therefore on your website’s carbon footprint. Choosing a web host that is proactive about software upgrades can help your environmental efforts.

Make your website more lightweight

The average size of a website home page in 2021 is 1.5 Mb (source: a manual check of 24 random client websites). That’s quite a heavy payload of data for the server and network to ship to a visitor. Anything that can be done to reduce the size of your pages will help not only your green effort but also means your site will load faster for your customers. This, in turn, will encourage search engines to rank you a bit higher too.

Good for the planet, good for your visitors, and good for Google! Happy days.

So, here are a few pointers for reducing website page sizes:

  • Compress your page content – this is effectively just getting your web server to ‘zip’ up the page before transmitting it to your visitor browser. The browser then unzips the page to display it to your visitor. Test your website to see if it is compressed here, and ask your web hosts to enable compression if it isn’t.
  • Keep your image sizes down. Do this by keeping their size as close as possible to the size they are displayed at on your website (i.e. don’t upload a 3000px wide image if it is going to be displayed in a 300px width sidebar!). Make sure that your images are optimised (compressed) to remove unnecessary metadata. Run them through an image optimiser (such as prior to uploading to your site, or use an image optimisation plugin (if you are using WordPress).
  • Use modern image formats, such as .webp, instead of .png, .gif, and .jpg files where possible. The webp format was developed by Google and allows your images to have the same quality, but with a lower file size than conventional images.
  • Cache your page content to make the finished page size smaller. Some web hosts cache content automatically, but there are some really good caching plugins for platforms such as WordPress, which also allow you to minify your content (by removing unnecessary spaces and comments) as well as caching a copy of your page(s) on the server so that they can be more quickly served to your visitors.

Which websites impact global warming the least?

If you are interested to know which organisations have the biggest website carbon footprint, and which websites impact global warming the least, take a look at the study carried out by earlier in 2021.

The study shows way out in front as the cleanest of the largest websites. Considering that their website is heavily text-based, with a relatively small number of large images, this isn’t surprising. Our own DMJ website would comfortably fit into the Top 10 of most carbon efficient websites… if only we had the traffic volume to match!

List of 25 websites impact global warming in the least way

The cleanest sites on the web – Image and figures courtesy of

Summary – keep it lean and host it green to improve your website’s carbon footprint

Overall, consider building a cleaner, less graphics-heavy website, with fewer unnecessary external calls. As well as doing your bit to save the planet, your visitors will appreciate how quickly your website loads, and how fast they can get to the content they are interested in. This, in turn, should help your SEO and help you to convert more visitors to customers.

If you can provide content in a form that gives visitors exactly what they want, they won’t need to bounce back to Google and look for other websites. Saving power, cutting web miles, and gaining a fan or two yourself!

Having built a lean website, go and look for a web host who has strong green credentials and a progressive approach to server upgrades.

This website is hosted Green - checked by

Let us know if you are concerned about the green credentials of your website

Drop us a line in the contact form at the bottom of this page if you want to improve the carbon footprint of your website.


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