One day, the internet will be powered by renewable energy. Until that day comes, there’ll be a CO2 cost that comes with every byte of data that’s uploaded or downloaded. By being able to calculate these emissions, developers can be empowered to create more efficient, lower carbon apps, websites, and software.

CO2.js is a JavaScript library that enables developers a way to estimate the emissions related to use of their apps, websites, and software.

Being able to estimate the CO2 emissions associated with digital activities can be of benefit to both developers and users.

Internally, you may want to use this library to create a carbon budget for your site or app. It is also useful for inclusion in dashboards and monitoring tools.

For user facing applications, CO2.js could be used to check & block the uploading of carbon intensive files. Or, to present users with information about the carbon impact of their online activities (such as browsing a website).

The above a just a few examples of the many and varied ways CO2.js can be applied to provide carbon estimates for data transfer. If you’re using CO2.js in production we’d love to hear how! Contact us via our website.

You can install CO2.js as a dependency for your projects using NPM.

npm install @tgwf/co2

You can import the CO2.js library into projects using Skypack.

import tgwf from "https://cdn.skypack.dev/@tgwf/co2";

You can get the latest version of CO2.js using one of the content delivery networks below.

You can find the package at https://www.jsdelivr.com/package/npm/@tgwf/co2.

• CommonJS compatible build https://cdn.jsdelivr.net/npm/@tgwf/co2@latest/dist/cjs/index-node.min.js
• ES Modules compatible build https://cdn.jsdelivr.net/npm/@tgwf/co2@latest/dist/esm/index.js
• IIFE compatible build https://cdn.jsdelivr.net/npm/@tgwf/co2@latest/dist/iife/index.js

You can find the package at https://unpkg.com/browse/@tgwf/co2@latest/.

• CommonJS compatible build https://unpkg.com/@tgwf/co2@latest/dist/cjs/index-node.min.js
• ES Modules compatible build https://unpkg.com/@tgwf/co2@latest/dist/esm/index.js
• IIFE compatible build https://unpkg.com/@tgwf/co2@latest/dist/iife/index.js

You can also build the CO2.js library from the source code. To do this:

1. Go to the CO2.js repository on GitHub.

2. Clone or fork the repository.

3. Navigate to the folder on your machine and run npm run build in your terminal.

4. Once the build has finished running, you will find a /dist folder has been created. Inside you can find:

   • dist/cjs - A CommonJS compatible build.
   • dist/esm - An ES Modules compatible build.
   • dist/iife - An Immediately Invoked Function Expression (IIFE) version of the library.

Type definitions for CO2.js are published in the DefinitelyTyped project, and are available on NPM at @types/tgwf__co2.

If you want to use type definitions in your project, they should be installed as a devDependency.

npm install --dev @types/tgwf__co2

CO2.js includes yearly average grid intensity data from Ember, as well as marginal intensity data from the UNFCCC (United Nations Framework Convention on Climate Change). You can find the data in JSON and CommonJS Module format in the data/output folder.

You can import annual, country-level marginal or average grid intensity data into your projects directly from CO2.js. For example, if we wanted to use the average grid intensity for Australia in our project, we could use the code below:

import { averageIntensity } from "@tgwf/co2";
const { data } = averageIntensity;
const { AUS } = data;
console.log({ AUS });

All countries are represented by their respective Alpha-3 ISO country code.

We use np to publish new versions of this library to NPM. To do this:

1. First login to NPM by running the npm login command in your terminal.
2. Then run npx np <VERSION>.
3. np will run several automated steps to publish the new package to NPM.
4. If everything runs successfully, you can then add release notes to GitHub for the newly published package.

CO2.js releases will be communicated through the following channels:

The code for CO2.js is licensed Apache 2.0. (What does this mean?)

The average carbon intensity data from Ember is published under the Creative Commons ShareAlike Attribution Licence (CC BY-SA 4.0). (What does this mean?)

The marginal intensity data is published by the Green Web Foundation, under the Creative Commons ShareAlike Attribution Licence (CC BY-SA 4.0). (What does this mean?)

See LICENCE for more.

Chris Adams 💻	fershad 💻 📖 🚧	Peter Hedenskog 💻	Dryden 💻	Evan Hahn 💻 ⚠️	Prathum Pandey 🐛 💻	Frazer Smith 💻 ⚠️
Hamish Fagg 💻	Atul Varma 💻	Piper 💻	Raymundo Vásquez Ruiz 💻	JamieB 💻	p-gerard 🐛 💻	Simon Fishel 💻