How we calculate emission

How we estimate carbon emissions

Understanding and reducing the carbon footprint of websites and apps is a crucial aspect of digital sustainability. To facilitate this, we utilize CO2.js, a tool developed by The Green Web Foundation. This JavaScript library allows us to estimate the carbon emissions associated with the data transferred during the usage of your digital products. This feature provides real-time carbon footprint analytics, empowering you to minimize your digital products' impact on the environment.

CO2.js and the Sustainable Web Design Model

CO2.js employs a model known as the "Sustainable Web Design" (SWD) model to estimate carbon emissions. This model considers various factors including the energy requirements of end-users interacting with a product or service, the energy required to host a product across servers, cloud containers, and content delivery networks, and the embodied energy and materials required to produce a product or service.

The SWD model uses kWh/GB as the key metric to calculate the carbon footprint. It uses the global average carbon intensity of electricity (442g/kWh) as the default figure for carbon intensity. However, this can be replaced with numbers for a specific country or state where this is known.

How We Calculate Carbon Emissions

When a user interacts with your website or app, data is transferred over the internet. We calculate the size of this data in bytes and use CO2.js to estimate the associated carbon emissions. This includes actions like downloading a file or loading an image.

We understand that the carbon intensity of electricity can vary greatly from country to country. Therefore, we take into account the country of origin of each user request. Using CO2.js, we get the grid intensity data for the specific country and use this to make more accurate carbon emissions calculations.

We aggregate the data from all user requests, taking into account the total number of requests, their transfer size, and the country of origin. This allows us to calculate the total carbon emissions associated with the usage of your website or app.

Reporting and Monitoring

We use the data from CO2.js as part of our internal monitoring tools and dashboards. This allows us to track the carbon emissions of your digital products and take action to reduce it where necessary.

In addition to these, we have developed specific metrics to better understand and reduce our carbon footprint:

  • Emission Per Page (EPP): The average amount of carbon emission generated by a page for a single user.
  • Cache Ratio (CR): The percentage of requests that were served from the local browser cache, providing insights into the efficiency of your website's caching.
  • Renewable Hosting Ratio (RHR): The amount of data sent from the server using green energy, helping you understand how much of your website's data is transmitted using environmentally-friendly hosting solutions. We also measure Total Emission, Transfer Size, and Emission Per User. Furthermore, we track first-party and third-party requests, providing a full list of requests, including their transfer size and carbon emissions. This allows us to identify which components of your website contribute the most to your carbon footprint and make informed decisions about optimizations.


By using CO2.js and the Sustainable Web Design model, we are able to estimate and monitor the carbon emissions associated with the usage of your websites and apps. This is a crucial part of our commitment to sustainability and reducing our carbon footprint. Our Realtime Carbon Footprint Analytics feature empowers you to take action, reduce your impact on the environment, and work towards a greener future.