Emission Per Page

Emission Per Page (EPP)

As the digital world continues to expand, so does its carbon footprint. Every website visit, every image loaded, every video streamed - it all contributes to the overall environmental impact of the internet. To help combat this, a new metric has been developed: Emission Per Page (EPP). This innovative metric is designed to measure the carbon emissions of a website, providing developers and businesses with the tools they need to understand and reduce their digital carbon footprint.

What is Emission Per Page?

Emission Per Page is a metric that quantifies the amount of carbon dioxide equivalent (CO2e) emissions produced by a single page load on a website. It takes into account the amount of data transferred over the network, providing a tangible measure of a website's environmental impact.

Why is Emission Per Page Important?

The internet's carbon footprint is significant and growing. Data centers, network infrastructure, and the devices we use to access the web all consume energy, much of which comes from fossil fuels. By measuring the EPP of a website, we can start to understand the environmental impact of our digital products and services. This understanding allows us to make informed decisions about how to design and build more sustainable websites.

How is Emission Per Page Calculated?

The EPP metric is calculated using a three-step process:

  • Track Requests: The first step is to track all requests for a specific pathname on a website. This includes everything from HTML, CSS, and JavaScript files to images, videos, and other media.

  • Sum the Transfer Size: The next step is to sum the transfer size of all these requests. The transfer size is the amount of data that is sent over the network to load the page.

  • Calculate Emissions: The final step is to run the total transfer size through the CO2.js library created by the Green Web Foundation. This library uses data on the carbon intensity of electricity and the energy intensity of data transfer to calculate the CO2e emissions associated with the data transfer.

Reducing Emission Per Page

Reducing a website's EPP involves optimizing the amount of data transferred to load a page. This can be achieved by:

  • Optimizing Images and Videos: Compressing images and videos can significantly reduce their file size without noticeably affecting quality.

  • Minifying and Compressing Code: Minifying HTML, CSS, and JavaScript files removes unnecessary characters (like spaces and comments), reducing their size. Compression further reduces file size by encoding the data more efficiently.

  • Leveraging Caching and Content Delivery Networks (CDNs): Caching stores copies of files in locations closer to the user, reducing the amount of data that needs to be transferred over the network. CDNs distribute these cached files across a network of servers, further reducing data transfer.


Emission Per Page is a powerful tool for understanding and reducing the environmental impact of our digital activities. By measuring and optimizing this metric, we can create a more sustainable web that benefits not just our users, but also our planet.