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November 2022
, by
Kuba Jawor

Building WordPress Websites in a Sustainable Way

The global number of internet and digital services users is growing exponentially. The demand increases faster than network (hardware, infrastructure) efficiency is improving therefore energy consumption to meet this demand is growing rapidly. This directly translates to a Carbon Dioxide (CO2) emission increase. It is estimated that about 2% of global CO2 emissions come from the internet, putting it next to the most polluting countries and industries like global aviation and shipping.

But how can we measure a website's CO2 emissions? There are many factors with different influences on the emissions but the easiest and directly measurable one (which can also be used as a representative of a website efficiency) is the actual website’s size. Taking the amount of data that is needed to fully load a website we can assess how much energy it requires and how much CO2 is being emitted to fulfil this energy demand. The bigger the files the more data is going to be transferred and stored and this means more energy consumption.

WordPress, being the most popular and widely used Content Management System (CMS) with about 40% of all websites using it, has a great impact on these numbers and therefore great potential to reduce the internet's carbon footprint. 

There are several, easy to implement general solutions and approaches to use whilst building a sustainable website.

Image conversion and compression

Data-rich visual assets like images and videos are responsible for the majority of total website size so making sure that we optimise these is crucial to significantly reduce its weight. 

  • Use modern image and video formats like WebP, WebM, MP4,
  • For icons and simple graphic elements use SVG,
  • If using PNG/JPG files, make sure to optimise/compress them.

When using WordPress, it is vital that resizing and compressing files happen 'on the fly’ when someone edits/adds content to WP. The go-to tool for this is Shortpixel AI - it automatically resizes images to appropriate use cases, compresses and converts JPG to WebP if the browser supports this format.

Browser-level image lazy-loading

Staying on the ground of the most requested and bandwidth-hungry assets (which images undoubtedly are) there is also widely supported by browsers loading attribute that we can use to further reduce page load size. If correctly implemented, this will allow loading images that are not in the viewport only when the user scrolls near them. Correct implementation would require including height and width attributes on the img tag so the browser knows the size of the image, therefore, can determine its distance from the viewport. It’s also a good practice to include these attributes anyway :)

<img src="image.png" loading="lazy" alt="…" width="200" height="200">

Thanks to the latest improvements of this feature in Chrome, its behaviour is now close to the one offered by JavaScript lazy-loading libraries. And because it’s done at browser level, we don’t need additional JS libraries which saves us even more on site size budget.

Read more here: https://web.dev/browser-level-image-lazy-loading/

Font optimisation

Single font file size can reach as much as hundreds of kb in weight. If we use more than one font on our website, the amount of data related to their size can grow significantly (in some cases, the size of one font file may be bigger than the whole front-end codebase of the website). 

The first step to reduce the size is to convert any ttf or otf font files to modern, web-focused formats like woff2. Only this can save us up to 25%. 


Going further, we can get rid of unnecessary characters. If the font file contains 2000 characters for many languages and our website needs only a fraction of this, we can strip the font file from any not-needed characters. 


Both techniques could save us up to 95% of the initial font file size.

Remember: any changes to the font must comply with the font's EULA.


Modern CSS and browsers give us solutions that quite easily can replace some of the JavaScript implementations (like mentioned earlier lazy-loading). The advantage of using these in favour of JS-based is that it minimises the client’s resources (like CPU usage) to achieve the same goal. CSS animations can do the same job with much less strain on the user's device. 

The general recommendation would be to use JavaScript with care and only there, where there is no other way of achieving the goal. This also applies to using any JS framework like jQuery or React. Before we start building the website, we should carefully and critically think if we actually need to use the framework/library we want to use or we just use it because we always do it? jQuery can be easily replaced with modern JavaScript and that alone would save us lots of data to be loaded on the website.

Compress the code

Using build tools to compress the code is another way to cut down file size which is being used as a production version. It strips the code from comments, unnecessary spaces and lines, therefore, reducing the size of the files. There are many tools available (like webpack or gulp.js to mention the most popular ones).

Stay static

With the core idea of any CMS being the solution for easy content management (hence the name) and dynamically displaying this content, to mention ‘static’ might sound out of place. But the big issue with all dynamic CMS solutions is that the content is being generated every time the page loads. That is a lot of data to be fetched from servers and many server calls to be made. But luckily there are tools and approaches to take to limit the problem or even completely change the way the website is served.

Page caching

To prevent every part of the page from being loaded from the scratch every time the user visits it, the easiest and most effective way is to set up page caching. This can be done on two layers: hosting (server) and CMS.

Server-side caching is the most beneficial as it sends the cached files directly to the user without querying the CMS. This saves energy, bandwidth and reduces page load times.

This feature is widely used by WordPress specific hosting providers like WPEngine and Kinsta.

If we implement page caching on the CMS layer, it will still have to generate all the content before serving cached files. But this solution is much easier to implement if our hosting provider doesn’t support server-side caching as we can use the WPRocket or Cloudflare Automatic Platform Optimization for WordPress plugins and also benefit from serving cached static files.

Go headless

A growing in popularity approach that helps tackle the dynamically generating web pages inefficiency is using JAMstack to build headless CMS solutions. JAM stands for JavaScript, APIs, Markup and it is used to separate adding and editing content from displaying it on the user front end. In essence, the CMS is only live when a user is logged in and is adding or editing content. After that’s done, the CMS generates static files and it’s not actively running anymore. This allows the pages with dynamic content to be served statically with all the benefits of static websites - better performance, security and energy efficiency as there is no need for the CMS to be constantly running on the server. Such solutions often use CDN (Content Delivery Network) to host the static files and therefore add even more energy-saving benefits by shortening the distance of data transfer (the farthest it has to go, the more energy is used to do it) and making the website more resilient by removing any single point of failure.

Use WordPress plugins and themes carefully

While a wide selection of plugins for WordPress is undoubtedly one of the key factors that built and maintains the platform’s popularity by extending its functionality to meet certain users’ criteria, excessive and uncontrollable use of plugins can have a negative impact on the website performance. Some might push extra scripts they need to the frontend not knowing that this script is already there and effectively doubling the scripts up and having a negative impact on efficiency and sustainability as well as slowing the site down. Even disabled plugins take extra space and might still have some impact on the website so it is strongly recommended to completely uninstall (not only deactivate) unused ones.

A similar, conscious approach applies to the use of ‘all-in-one’ WordPress themes. As much as they might be seen as the easiest solution to apply a non-standard theme to our website and give us flexibility, they are often (because of their universal nature) bloated and consist of features that we don’t need and will never use. But it’s there, in the code and the structure, making the theme and therefore the whole website big and slow.

We hope you have enjoyed this deep dive into improving the digital sustainability of your next WordPress build. If you are keen to learn more about the L+F approach to sustainability on the web, we'd love to hear from you.



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