My Mission

A More Efficient Web

Motivation

Sending data over the internet consumes energy, much more than I anticipated before delving into the topic. A megabyte of transmitted data can cost tons of CO₂ when sent to enough visitors (see calculation). Additionally, high data loads can result in long wait times for content to be displayed on a webpage. In fact, measures to optimize web performance and web sustainability are almost congruent as the diagram below illustrates.

We can save energy through more efficient websites, while also reducing the time visitors spend waiting for their content. Everyone wins: website owners, visitors and the planet! I don’t want to go as far as claiming we’re saving lifes, but that’s actually how it was communicated within Google’s teams, when they were trying to speed up their services:¹

The calculation goes like this: the average human life expectancy is seventy years. That’s about two billion seconds. If a product has 100 million users and unnecessarily wastes four seconds of a user’s time every day, that was more than a hundred people killed in a year.

While this calculation is ethically questionable, it illustrates the point well. We should not take the loading time of our web content lightly.

Prolonged waits for content cause visitors to lose sight of their original intention.² Visitors are easily distracted, a phenomenon that is exacerbated by increasingly shorter attention spans.³

Why then are not all websites optimized down to the last kilobyte? Well, only in recent years awareness of how the speed/performance of a website affects user behavior has been growing. Neither performance nor resource consumption were criteria in web product specifications and often it’s still lacking to date. Slow web content is often optimized only when the published content is too slow. The optimizations then improve the status quo but often fail to create a sustainable change in work processes. I want to help effect a change in mindset.

CO₂ Calculation Example

We can use the open-source library CO2.js to estimate how much the data transfer alone from a server to its visitors costs.^c

Let’s look at the website of German news portal Der Spiegel. Since we’re only interested in the rough scale of carbon emission, I want to make a few simplifying assumptions.

• All visitors only access the homepage.
• 1% of all visitors access the page uncached (first visit after a long pause)
• All visitors accept the privacy conditions.
• All visitors scroll down to the first video section.
• No Ad-Blockers are used.
• Everyone gets the same ads as I did in my tests (nothing personalised, no changes over time).

I conducted tests using Chrome on my laptop with a mobile device emulation.

During the initial loading, accepting the privacy policies and scrolling of the website, there was a data transfer of 8.4 megabytes. However, during a subsequent visit just one day later, this was reduced to 4.2 megabytes, which is exactly half the payload.

Fortunately, hosting of the website is green,⁴ resulting in some CO₂ savings.

However, the transfer of data per page view costs 447mg CO₂.^d Now, let’s calculate with 166 million visits per month.⁵ This leads to 890 tons of emitted CO₂ per year and corresponds to the stored CO₂ of 40.000 mature trees.^e 🤯

While the numbers may seem staggering, the good news is that there are achievable solutions that could significantly reduce these emissions, even on a conglomerated website like spiegel.de

Simple Optimization Works

Especially for high-traffic websites, small changes can have a huge impact. In the example calculation above, saving 2MB of data for new visitors and 1MB for returning visitors would mean a saving of 213 tons of CO₂ per year.^f That’s more than 27 times as much as an average European person consumes⁶ or as much as 10,000 mature trees can store in a year. And the good news is, it wouldn’t be difficult to achieve such savings. Thus, making a real difference by just making sure best practices are followed.

How We Can Effect a Change in Mindset

The problem is not a lack of willingness to save CO₂. Rather, it’s a lack of awareness regarding the CO₂ emissions of websites. So, better communication is needed. I’m pleased to see that the W3C has established a working group on sustainability, which defined guidelines on the topic in the fall of 2023.⁷ I hope that such an authoritative institution in the web will generate the necessary attention. The concept of sustainability here is much broader than just ecological and aligns with the definition of the Sustainable Web Manifesto,⁸ which I have signed. Sustainable web development is thus:

• Clean (based on renewable energies)
• Efficient (uses as little energy as possible)
• Open (accessible and privacy-protecting)
• Honest (no misleading content)
• Regenerative (supports sustainable economies)
• Resilient (robust and secure)

Since many website operators primarily care about their own profitability despite the reasons mentioned, it is a blessing that performance and sustainability are closely intertwined. It is easier to convince when there is a correlation between web optimization and the success of the website.^g