Technical Adjustments for More Sustainable Websites

Climate change is a hot topic of conversation. This often involves looking at, for example, the effects of aviation, transport and agriculture. What far fewer people know, however, is that the digital world also has a significant impact on the climate.


Almost all scientists agree that humans are responsible for climate change. The consequences of this will have significant consequences for humanity. Some examples of the consequences of climate change are persistent drought, rising sea levels, less biodiversity, and damaged ecosystems. But, what does the foregoing have to do with website optimization?

Impact of digital on climate

The digital sector plays an important role in causing global warming. It is estimated that this sector is responsible for approximately 2-4% of global greenhouse gas emissions. A percentage comparable to global aviation.

It can be difficult to understand why the digital industry produces such large greenhouse gas emissions. Unlike an airplane or car, a laptop or mobile phone does not have an exhaust. However, what can help is to look at the entire lifecycle of a product. A distinction is often made between the phases: production, consumption, and end-of-life.

Product lifecycle
  • Production: The production of all appliances emits greenhouse gases and uses large amounts of water. This applies not only to laptops, tablets, and mobile phones, but also to servers, monitors, keyboards, etc. For example, estimates indicate that mining raw materials and converting them into a new laptop emits approximately 330 kilograms of CO₂ and 190,000 liters of water are used.
  • Consumption: Using appliances requires electricity and cooling. Worldwide, a large percentage of the total electricity generated still comes from fossil fuels (such as coal and gas). The result of the foregoing is that the use of appliances creates a demand for more electricity, which is then largely supplied by the use of fossil fuels.
  • End-of-life: After a consumer decides he no longer needs a device, it is sometimes (partially) recycled, but usually the device is destroyed. Not only does this destruction require energy (such as gas or electricity), but additional harmful substances can also be released that have a negative effect on the climate.

The role of websites

When someone requests a website, the server on which that website is located often has to retrieve and process data. This not only applies to human visitors, but also to search engine spiders. The retrieved data must then be sent over the network to the users' device. The device must then receive this data and display it in the browser. All these steps require energy. This ensures that every page view results in greenhouse gas emissions. Scientists do not yet agree on the exact amount of emissions per page. However, there is agreement that various steps can be taken to reduce the impact.


It is important to realize that although the examples below have been collected with care, their effectiveness depends on their context (technology, employees, etc.). Therefore, consider having a website analysis carried out. The points below (among many other matters) will be examined in detail for your specific situation.


The examples discussed later in this article have several positive consequences. In this way they reduce the size of a page, so that less data needs to be sent. They also contribute to the fact that (parts of) web pages do not have to be retrieved from the server each time. These best practices also ensure that the users' device does not have to work as hard to get the website on the screen.

Benefits for companies and users

All these factors ensure a faster loading speed of the website or webshop. As shown in case studies from Microsoft, Firefox, Amazon, and Walmart, among others, better loading speed leads to a higher conversion rate. In addition to benefits for the user experience and sustainability of a website, Google has also publicly indicated that loading speed is an official ranking factor in their ranking algorithm.


Below are some concrete examples of how websites and web shops can become more sustainable with the help of technical adjustments. This includes using ideas described in the book Sustainable Web Design by author Tom Greenwood.


Every website or webshop is hosted somewhere on one or more servers. These servers are usually located in huge data centers. Because these data centers require a lot of electricity and cooling, it is important which sources they use for this. With the help of Green Web Check you can get an idea of whether a particular web host uses green energy. A point of attention is that there appears to be little external validation, so it may be a good idea to contact a hoster about this if you have any doubts. In addition to choosing a specific hosting party, technical adjustments can also have a positive impact. For example, consider using a CDN such as Cloudflare, which means that the data does not have to travel as far from the server to the user.


With caching you prevent that every time a page is viewed, it has to be retrieved, processed and sent again. There are several different ways you can cache web pages and resources on them. For example, you can cache resources such as JS/CSS files or images for a certain period of time. It is also possible to cache things such as HTTP headers so that they do not have to be resent with every request. The most complete form of caching is called full page caching. An entire web page is temporarily saved so that it can be served immediately. This ensures a very fast charging time and also a minimal impact on the climate.

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Nowadays, websites increasingly use JavaScript. Popular Single Page Application frameworks such as React and Angular are well-known examples of this. By building websites client-side using such SPA frameworks, part of the required processing power is shifted away from the efficient and powerful web servers and towards the users' devices. All this processing by devices that are not optimized for this requires a relatively large amount of power and therefore has a negative impact on the climate. The above applies in particular to mobile devices.


Previously, it was believed that watching online videos had a huge impact on the climate. However, a recent analysis by the IEA shows that although the impact is significant, with an average of 36 grams of CO₂ per hour of video, it is much less significant than older analyzes seemed to show. However, these 'limited' emissions compared to previous estimates do not mean that the role of video in optimizing websites should be underestimated. First of all, you need to consider from which location the video is loaded. Although the majority of websites nowadays choose to host videos on websites such as YouTube and Vimeo, you sometimes come across so-called self-hosted videos on servers that are not optimized for this. A lot of loading time can also sometimes be saved by things such as removing or reducing background videos. Using a so-called facade instead of loading a video directly can also yield positive results.


Almost every modern website contains one or more photos. Although a photo sometimes says more than a thousand words, it certainly results in many more greenhouse gas emissions and a slower loading time. It is therefore important to think carefully about how photos are used. For example, photos often add little to the website. Maybe these photos can be taken down? You can also consider compressing the photos and/or using a modern file type. In addition to these previously mentioned methods, lazy loading can also be an effective method to significantly reduce the impact of photos on loading time and emissions.


The digital world has a significant impact on the climate change that is underway. However, by using techniques as described in this article intelligently, the impact of websites on the climate can be significantly limited. An additional advantage is that in many cases these techniques can also ensure a faster loading time, which can then have positive consequences such as increasing the turnover of a webshop or improving the rankings in Google.

About the author

Theo van der Zee (MSc, Psychology) has been building and optimizing websites and web shops for more than 20 years. As a freelance conversion specialist, he helps companies to improve their websites based on research and experiments.

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