Photo of wind turbines in a field
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The why of website optimisation: Help the planet

This is the third post in a series where I'll outline the benefits that can be derived through website optimisation. Not only will we touch on monetary aspects, but we'll also get into environmental impact, and customer experience.

You can read the other posts in this series using the links below (they'll be at the end of this post too):

  1. Increase conversions (or engagement)​
  2. Reduce operational costs​​
  3. Reduce environmental impact​ - This post
  4. Improve your search ranking​
  5. Deliver a better user experience​

Now, let's get onto how optimising your site can help you reduce its carbon footprint, and go a little way to helping the environment.

Data does create CO2

Data creation, storage, transfer, and consumption all use electricity. Although it’s not as tangible as fumes from a car, each site on the internet contributes to global CO2 emissions.

Looking at an average web page size of 4MB, it is estimated that a page of this size creates approximately 1.6 grams of CO2 each time it is visited by a user. Over a year, if this one page is visited 600,000 times it will produce 10KG of carbon emissions. (Source: World Wide Waste, Gerry McGovern). These figures are for a single web page. Most websites consist of multiple pages, and many are larger than the 4MB average. So, the overall yearly carbon footprint of a website might be in the 10s, if not 100s, of kilograms.

What should we aim for?

Google recommends web pages be around 500kB in total size. At the time of writing, HTTP Archive were measuring the median size of images on the web pages at around 1000kB (1004kB for desktop, 920kB for mobile). So, optimise your images and use the latest formats (with fallbacks) whenever you can. Please.

Getting a website down to one-eighth of its previous size is a heck of an ask. But even just getting page size down to 1MB would allow us to reduce up-to 75% of the CO2 emissions that are created when the page is accessed. Sure, there's still a carbon footprint from hosting and running services in the cloud, but a relatively easy to achieve 75% cut in CO2 emissions is something we should all strive for.

Clean code can help too

I don't have much to say here, I'll just leave this quote here from Gerry McGovern (again).

By cleaning up its JavaScript code, Wikipedia estimated that they saved 4.3 terabytes a day of data bandwidth for their visitors. By saving those terabytes, we saved having to plant almost 700 trees to deal with the yearly pollution that would have been caused.
~ Gerry McGovern, World Wide Waste, 2020

Here's a link to an article with more details.

How can I check my website's carbon footprint?

Wholegrain Digital have built the incredibly handy Website Carbon Calculator for just this purpose. Put in a URL, and it will analyse both the web page itself and hosting provider to determine how much CO2 is produced per visit. It also presents some handy examples to put things in scale.

If you'd like to switch to a green web host, then The Green Web Foundation has a list of globally available green hosting companies that you can check out.

Read other posts in this series for even more reasons to optimise your websites.

  1. Increase conversions (or engagement)​
  2. Reduce operational costs​​
  3. Reduce environmental impact​ - This post
  4. Improve your search ranking​
  5. Deliver a better user experience​

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