Site speed optimization reduces bounce rate and CO2 emissions

Site speed case study
Our work with a personal care brand to improve site speed reduced the bounce rate of UK pages by 13% and cut CO2 emissions by 355kg per year.
Sustainable Web Manifesto“If the Internet were a country, it would be the 7th largest polluter in the world.”


One of the world’s largest Beauty and Personal Care brands, with a key strategic goal to amplify what the brand does in line with creating long-term societal and environmental change, asked us to work on a variety of projects to help them improve site speed and determine the benefit of site speed optimization to the business.


We used synthetic testing and real user monitoring (RUM) to analyze performance bottlenecks, developed a method to calculate carbon emissions generated per page visit, and created a strategic approach to performance monitoring, which included a new set of KPIs.


We identified the reasons for poor speed, provided a prioritized set of fixes, supported the client’s tech team in implementing optimizations, and calculated the monetary value of site speed improvements and the extent to which site speed improvements reduced carbon emissions.


We worked closely with our client and their tech supplier on a 3-month sprint, which resulted in reducing load time by an average of 21% across 60 markets. Bounce rate dropped significantly: between 8% and 28% across all the markets that we analyzed and the improvement in speed was estimated to be worth more than £333K in the first year across 4 key markets alone. Site speed for UK pages improved by 50% and bounce rate reduced by 13%.

We looked at the environmental impact of multiple sprints that comprised a program of optimization. The environmental impact was also significant. The reduction in CO2 emissions was estimated to be 355kg for mobile visits to UK pages alone, in the first year post-optimization, and the energy saving was enough to drive an electric car 4,799 km and make 48,063 cups of tea.

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