Connect, not collect
�Making digital sustainability standards discoverable with carbon.txt
GREENWEB.ORG
Chris Adams
14.11.2025�EcoCompute 2025
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Hello, I’m Chris!
My background:
�Loco2 - Low CO2 Travel in Europe by train
A.M.E.E (Avoid Mass Extinction Engine) - CO2 calculation as an API
Green Software Foundation - policy working group co-chair, leading the new SCI-Web standard
Branch Magazine - contributor, co-founding editor
ClimateAction.tech - community organiser since 2018
Environment Variables podcast - host since 2022
Green Web Foundation - director of tech and policy (my day job)
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GREEN WEB FOUNDATION
The Green Web Foundation is working towards a fossil-free internet by 2030.
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The internet should be a global public good, and a tool for liberation. Healthy for the planet and for the people who use it.
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What we’ll cover
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View source, and why I love the web
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Have you ever done this?
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Every single web page you visited contained the code showing you how it was created. The entire internet became a library of how-to guides on programming�
From Coders, by Clive Thompson
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When you render the page, you demonstrate that your code is behaving the way you said it would. ��You’re backing up your claim.
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Webby claims, and what they are
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Security and HTTPS connections
Look for the padlock
Highlights that the connection is secure between your browser and the server you’re connecting to.
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The claim:
“The connection between your browser and this site is secure”
Backing it up:
��Checking the padlock, and where the linked certificate comes from*
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* yes, it’s more complicated than this, but if there’s no padlock, you’re not connecting over HTTPS
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Web Performance
Various metrics are now used to track performance of a website.
Examples:
First Contentful Paint - when the first element on a page is rendered
Total Blocking Time - broadly, how long a page spends loading before it can respond to user input
Speed Index - how quickly the layout is visually displayed
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The claim:
“My site is fast loading.”
Backing it up:
�Lighthouse score of at least 90, across 5 metrics.
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Web accessibility
W3C Web Content Accessibility Guidelines - WCAG
A set of recommendations for people building websites to make them available to people with accessibility needs.
Public sector websites** in many countries now require an accessibility statement stating the level of accessibility they target, and how to report problems.
** the European Accessibility Act came into effect in June this year. You might need this for your site too now.�
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The claim:
“My site is wholly compliant with Web Content Accessibility Guidelines version 2.2 AA standard”
Backing it up:
�Site does not fail* with accessibility checking tools, like Deque’s AXE, the Lighthouse checks we saw before, or built-in browser checkers, etc
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* it is more complicated than this, but if a site doesn’t pass these automated checks, the claim definitely isn’t in true�
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Applying webby claims to digital sustainability
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The claim:
“Our websites run on green energy”*
* green is a loaded term. You can still be green and evil. We mean annually matched with renewable energy certificates for the most part. See our blog for more.
Backing it up:
�Finding out where the server is run.�
Seeing what evidence the operator has shared.��Linking to evidence in the public domain.
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This is broadly how our Green Web check works. ��We link domains to reporting entities and the public info they share with us
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Why do you have to trust us though?��Can the data be disclosed to make your own decisions?��We’ll come back to this with carbon.txt
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Did you see Frank from Nextcloud’s talk about Green Gates and energy disclosure earlier today?��
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The claim:
“Our software meets the Blue Angel Standard for transparency and sustainability”
Backing it up:
�Pulling out the key claims and user journeys.��Linking to the certification published on Blauer Angel.
Linking to the CI?
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The underlying details for Nextcloud’s sustainability claims does exist.��But you need to know to look for it.
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The claim:
“Our software has a Software Carbon intensity rating of 0.5g CO2 for the most common user journey of buying a widget”
Backing it up:
�Making clear what the user journey actually is.��Linking to your work, available in the public domain.��Linking to a hash if you can’t share all the data, so the original data can be audited
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The claim:
“Our software runs in green, sustainable datacentres”
Backing it up:
�Linking to a completed E.E.D submission in Europe. For Germany, the EnEfG (Energy Efficiency Law in Germany)
�💡 Top tip: Differentiate from your competitors by actually following the law - you’re supposed to do this anyway if you run a data centre above a certain size.
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The big idea behind carbon.txt
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The core idea
/carbon.txt* is a single place to look on any domain for machine-readable sustainability claims and data for that organisation.
Inspired by existing concepts like /robots.txt
* Yes, we support .well-known/carbon.txt too
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Extendable syntax, linked validation
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Tools to play with
Find at: https://carbontxt.org/tools
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Why start with the CSRD? Part of a trend.
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“Show us you track emissions, and share this info with society”
Corporate Sustainability Reporting Directive (CSRD)
Climate Corporate Data Accountability Act (CCDAA)
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CSRD: Carrots AND sticks
Report because it’s the law.
Large fines, and jail time if you don’t play ball, or say untrue things.
Consequences
Argument
Report to help raise money.
Missing out on cheap green finance to grow your business.
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Companies share shiny ESG reports all the time.��What if they had actually useful, linked, comparable information in them?
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Linking straight to a disclosed datapoint: ��scope 2 carbon emissions
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ESRS - European Sustainability Reporting Standards
General requirements and disclosures
ESRS 1
General requirements
ESRS 2
General disclosures
Environmental
ESRS E1
Climate Change
Social
ESRS E2
Pollution
ESRS E3
Water and marine resources
ESRS E4
Biodiversity and ecosystems
ESRS E5
Resources and circular economy
ESRS S1
Own workforce
ESRS S2
Workers in the value chain
ESRS S3
Affected communities
ESRS S4
Customers and end-users
ESRS G1
Business conduct
Governance
ESRS - European Sustainability Reporting Standards
General requirements and disclosures
ESRS 1
General requirements
ESRS 2
General disclosures
Environmental
ESRS E1
Climate Change
Social
ESRS E2
Pollution
ESRS E3
Water and marine resources
ESRS E4
Biodiversity and ecosystems
ESRS E5
Resources and circular economy
ESRS S1
Own workforce
ESRS S2
Workers in the value chain
ESRS S3
Affected communities
ESRS S4
Customers and end-users
ESRS G1
Business conduct
Governance
Omnibusification�
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Noun:�When transparency in a sector is placed into limbo for years because of regulatory capture by entrenched players “efficiency and �competitiveness”
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What if we’re not able to rely on the CSRD? Help us figure out a plan B.
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Wrapping up
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Key things I want you take away
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Thanks!�This deck is online, with links and more�https://thegreenweb.org/events/ecocompute-2025/
www.linkedin.com/in/mrchrisadams
mastodon.social/@mrchrisadams�
�P.S. Come to my table at the Innovation Cafe after lunch! I’m there for 3 hours 😅
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While I am here…��We have a few spaces left in our workshop next week!
Nov 18th �12:00 - 14:00 CET
Use the QR Code below
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Appendix�Slides dropped for time
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liberté�egalité�CSRDé
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Jargon soup in the CSRD
CSRD reporting uses the same XBRL language as other structured filings by companies. ��It uses a XBRL Taxonomy - a restricted catalogue of terms to refer to the kinds of data required. ��For the CSRD, there is an ESRS (European Sustainability Reporting Standards) taxonomy. ��Annual reporting in the should follow the ESEF (European Single Electronic Reporting File format),
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The fancy ESEF thing is really just HTML in a trenchcoat
XBRL - Extensible Business Reporting Language, a dialect of XML used for financial reports released in 2003.
XHTML - Extensible HyperText Markup Language - a dialect of XML designed for browsers to render, released in 2001.
XML
XBRL
XHTML
iXBRL
XML - extensible markup language. A common format designed for exchanging data
iXBRL - inline XBRL. An XHTML document with XBRL metadata embedded. Widespread use from 2010, by the UK, EU and USA.
The European Single Electronic Reporting (ESEF) format is in reality an existing format called iXBRL.
The SEC database in the USA, EDGAR, also uses this XBRL thing.
It has an official validator and renderer, with guidance on how to navigate errors.
As soon as your submission is validated, it goes into a public RSS feed of all filings.