GreenCheck

Overview

GreenCheck is a browser extension that helps users understand the environmental impact of the websites they visit. It identifies if a site is powered by renewable energy and estimates its carbon emissions, giving users instant feedback on a website's sustainability.

The Story Behind It

GreenCheck was inspired by a moment walking through Copenhagen in 2024, shortly after giving a talk for GlasgowJS about measuring web carbon output. I'd been using The Green Web Foundation to check if websites were powered by green hosting, but found the experience limited — it required manually entering each URL into a form.

I wanted something that worked passively in the background, surfacing this data where users already spend time — in their browser.

What I Built

GreenCheck makes the process frictionless. It:

• Adds 🌱 icons beside green-hosted sites directly in Google search results
• Dynamically changes the browser extension icon between green and red based on site energy source
• Includes a popup dashboard showing whether the current site is hosted sustainably
• Offers an in-extension “Scan” tab that analyzes page weight, estimated carbon usage, and grades the site from A to F

Technical Overview

The extension is built using:

• SvelteKit for a lightweight, reactive UI
• TypeScript for maintainable code
• TailwindCSS for rapid styling
• Plasmo Framework — “Next.js for extensions” — to streamline browser extension development
• Cloudflare Pages for hosting the website

The Problem It Solves

Most people don't think about the carbon footprint of the websites they use daily. Tools to measure this exist, but they aren't built for convenience or visibility. GreenCheck brings this awareness into users' browsing experience, helping them make more sustainable digital choices without extra effort.

Outcome

The result is a smooth, visually engaging browser extension that raises awareness of sustainable hosting — while serving as a great learning project in building with Plasmo and Cloudflare.

You can try it here:
👉 getgreencheck.com

Or explore the design prototype:
🎨 Figma File