Member Story
"How do you measure a website's carbon footprint?"
How Chris Adams of the Green Web Foundation and 14 assembly members from across the industry are building SCI for Web — a standard for measuring website carbon intensity that covers the full delivery chain: servers, networks, third-party services, and end-user devices.
Organisations involved
10 weeks
From blank page to consensus design document through AI-assisted assembly
14
Assembly members from 15 organisations — tech giants, data providers, academics, and practitioners
W3C
Formal collaboration with the world's web standards body — bridging two communities for the first time
The Problem
Web emissions tools existed — but results weren't comparable, boundaries weren't defined, and third parties were invisible
Almost everyone uses the web daily. Yet no standard existed for measuring a website’s carbon intensity. Tools like the Sustainable Web Design Model, CO2.js, and the W3C Web Sustainability Guidelines had made web emissions visible and established foundational methodologies that thousands of practitioners used. But as organisations moved from awareness to accountability, they needed something more rigorous: a measurement approach with clear boundaries, carbon per functional unit rather than totals, and disclosed methodology so results were comparable and defensible.
The fragmentation ran deep. Modern web applications depend extensively on third-party services — analytics, advertising, CDNs, authentication — which consume energy on both servers and client devices. Without a standard that defined what to include and how to attribute emissions across this chain, any measurement was partial. Organisations could not compare results, validate reduction claims, or make informed decisions about where to invest optimisation effort.
The Journey
From a measurement gap to a formal W3C collaboration and consensus design document
The web measurement gap becomes visible
2024–2025
As the SCI specification matured into ISO/IEC 21031:2024, GSF members recognised that a domain-specific, SCI-aligned approach was needed for web applications. The parent SCI standard was powerful but general. Web applications had unique characteristics — browser rendering, third-party dependencies, content delivery networks, user device diversity — that required specific guidance on boundaries and functional units. Tools like CO2.js and the Sustainable Web Design Model had made web emissions visible, but results weren't comparable and organisations couldn't validate reduction claims.
Beyond single-dimensional metrics for digital sustainability →W3C and GSF announce formal collaboration
September 2025
Chris Adams of the Green Web Foundation, active in both communities, brokered a strategic collaboration between GSF and W3C. GSF would manage the SCI for Web specification; W3C's Sustainable Web Interest Group would provide feedback. The collaboration included joint knowledge sharing, development of training materials, and Impact Framework templates. As the announcement stated: "Almost all of us use the web daily, and like everything else, we need to make using it more sustainable."
Read about the GSF and W3C collaboration →AI-assisted consensus assembly
September–November 2025
Fourteen GSF members piloted an AI-assisted assembly process. Participants answered structured questions about measurement accuracy and adoption complexity. An LLM synthesised responses into draft content. The group reviewed and refined through multiple rounds. In contentious areas, participants revised until all objections were resolved. In ten weeks, the assembly moved from a blank page to a consensus design document — resolving the core tension: "A specification that is technically accurate but unused won't serve its purpose, and a widely used metric that lacks credibility also won't serve the purpose."
About the SCI for Web assembly →Design document published
February 2026
The full consensus document was published. Scope: web applications delivering value through browser interfaces via HTTP/HTTPS, covering static sites, SPAs, server-rendered apps, e-commerce, and streaming services. Third-party services — analytics, advertising, CDNs, authentication — must be included within the measurement boundary because they consume energy on both servers and client devices.
Read the SCI for Web assembly report →SCI for Web specification accepted and launched
Q1 2026
The SCI for Web specification entered active development under the Software Standards Working Group, led by Chris Adams. Built on the consensus design document, the specification will define how to measure the carbon intensity of web applications across the full delivery chain.
Learn about the SCI for Web standard →Sustainable digital transformation is fundamentally about behavioural change, not just technical solutions. When colleagues understand that unused content with heavy PDFs and videos has a real environmental impact, they make more thoughtful decisions about what they create and maintain.
Emma Horrell, User Experience Manager, University of Edinburgh
Who came together
The people who made it happen
Chris Adams
Director of Technology and Policy
Green Web Foundation
Proposed SCI for Web, brokered the W3C collaboration as an active member of both communities, and leads the SCI for Web project.
Joseph Cook
Head of Research
Green Software Foundation
Designed the AI-facilitated consensus mechanism and facilitated the assembly process, enabling 14 experts to move from a blank page to consensus in ten weeks.
Alekh Gupta
Assembly participant
Participated in the AI-assisted assembly, contributing expertise to the consensus design document for SCI for Web.
Alexander Dawson
Assembly participant
ClimateAction.tech
Participated in the AI-assisted assembly, contributing expertise to the consensus design document for SCI for Web.
Camille Fassett
Assembly participant
WattTime
Participated in the AI-assisted assembly, contributing expertise to the consensus design document for SCI for Web.
Facundo Armas
Assembly participant
Globant
Participated in the AI-assisted assembly, contributing expertise to the consensus design document for SCI for Web.
Florent Morel
Assembly participant
Amadeus
Participated in the AI-assisted assembly, contributing expertise to the consensus design document for SCI for Web.
Francesco Fullone
Assembly participant
GrUSP
Participated in the AI-assisted assembly, contributing expertise to the consensus design document for SCI for Web.
Mathias Uhlitzsch
Assembly participant
Evosoft
Participated in the AI-assisted assembly, contributing expertise to the consensus design document for SCI for Web.
Nisha Ramachandra
Assembly participant
Accenture
Participated in the AI-assisted assembly, contributing expertise to the consensus design document for SCI for Web.
Raghava Rao Battina
Assembly participant
HSBC
Participated in the AI-assisted assembly, contributing expertise to the consensus design document for SCI for Web.
Riccardo Pomato
Assembly participant
Microsoft
Participated in the AI-assisted assembly, contributing expertise to the consensus design document for SCI for Web.
Ryan Sholin
Assembly participant
Electricity Maps
Participated in the AI-assisted assembly, contributing expertise to the consensus design document for SCI for Web.
Thiago Falcao Silva
Assembly participant
NTT DATA
Participated in the AI-assisted assembly, contributing expertise to the consensus design document for SCI for Web.
Daniel Schien
Assembly participant
University of Bristol
Participated in the AI-assisted assembly, contributing expertise to the consensus design document for SCI for Web.
Asim Hussain
Executive Director
Green Software Foundation
Participated in the AI-assisted assembly, contributing expertise to the consensus design document for SCI for Web.
In their words
"Almost all of us use the web daily, and like everything else, we need to make using it more sustainable. By defining a standard for measuring website emissions, we make it easier for people to request greener digital services, for responsible technologists to build them, and to reach the fossil-free internet we all need. "
GSF–W3C collaboration announcement
September 2025
"Tools exist to measure a website's carbon footprint, but every tool uses different boundaries, different assumptions, and gets different results. SCI for Web builds industry consensus on how to measure — so organisations can finally compare, validate, and act on the numbers with confidence. "
Asim Hussain
Executive Director, Green Software Foundation