carbon.txt makes sustainability data easier to discover and use on the web.
carbon.txt is a single, discoverable location on any domain – /carbon.txt – for public, machine‑readable sustainability data.
Organisations publish their data and let others know where to find it through their carbon.txt file. Meanwhile data consumers know where to look for these disclosures. Carbon.txt files become a vital link making it much easier for everyone.
Behind the scenes, it’s a web‑first, connect‑not‑collect approach, designed to be extended. We envisage carbon.txt growing into essential data infrastructure that supports meaningful action on the climate crisis.
Organisations sharing their sustainability data via a carbon.txt file demonstrate a real commitment to sustainability through being transparent. This approach allows more ambitious players to set new norms around disclosure.
Chris Adams, Director of Policy & Tech – Green Web Foundation
You can continually update your carbon.txt file as your reporting or data standardisation processes mature – that’s the beauty of the web.
Fershad Irani – Green Web Dataset lead – Green Web Foundation
We want TCS data to be easily retrievable by other systems for digesting, parsing, benchmarking and most crucially; transparency. This is exactly the value we see carbon.txt providing, and it allows us to focus our resources on getting the best possible data created in the first place.
Oliver Cronk – Technology Director – Scott Logic
Using carbon.txt
Example applications
Carbon.txt is already being applied in different contexts to create a positive impact. Explore these examples to see how it helps with recognition, compliance, and standards alignment.
Sustainability reports
Green claims
Digital emissions
Making a carbon.txt file
We’ve created a collection of guides and tooling to help organisations quickly get started publishing carbon.txt on their own websites.
Get started
Learn how to create a carbon.txt file for your organisation, upload it to your domain, and check to ensure it’s valid.
Builder
An interactive builder that will help you quickly create carbon.txt files that link to your organisation’s disclosures.
Validator
A syntax validator that checks the contents of a carbon.txt file, and shows the content that can be discovered through that file.
Using or extending the carbon.txt code
The tooling for reading and parsing carbon.txt files is open source and designed to be extended. Use and extend it to parse linked documents for new insights and data.
Get a technical overview
See a high-level explanation of the carbon.txt validator and its architecture, so you can use it in your own data pipelines.
Check out the code
Get the source code for the carbon.txt validator, to see how it works, and run it yourself.
Extend carbon.txt
Learn how to make plugins to extend the functionality of the carbon.txt validator, and work with new kinds of data for your use case.
We welcome contributions and info on how this tool helped you solve a problem.
Licensing
The code for carbon.txt is licensed Apache 2.0 (What does this mean?).
Getting Support
For technical questions or ideas please open an issue on the carbon-txt-site github repository – our chosen place for community support.
For a query about carbon.txt that you’re not comfortable sharing publicly, or for commercial support using any of the tooling around carbon.txt, please use our contact form.
Collaborate
We’re actively looking to work with:
- Organisations who want to make carbon.txt files to disclose their own data.
- Advisors on matters like structured sustainability data, especially green energy data and other standards this could be useful for.
- Tech teams who want to extend the carbon.txt code to do other cool things with data.
If you’re keen to have a conversation about carbon.txt, or to discuss our mission for a fossil-free internet in general we’d love to start a conversation. Please use our contact form.
News and updates
A core ethos of Green Web Foundation’s mission is that we work in the open as much as possible. Here’s some of our recent posts relating to carbon.txt.
- A *May* update on the first E.E.D. day in Europe
- Using carbon.txt with CSRD reports
- Using carbon.txt with the Technology Carbon Standard
- Green hosting providers can use carbon.txt
- Introducing our new work on carbon.txt – the carbon.txt validator and an updated spec
- Meet us at the 6th International Open Search Symposium in Munich in October
- EU sustainability regulation experts: can you help us?
- Introducing carbon.txt – Applying lessons from crowdsourcing net zero data
- How much of the internet is covered by credible Net Zero targets? What we learned
Project history
Sept 2025 – Integrated carbon.txt into the Green Web Dataset verification process. Learn how it works in our guide Using carbon.txt to improve Green Web Check results.
April 2025 – Collaborated on getting a Technology Carbon Standard (TCS) schema published, establishing a framework for reporting standardised digital sustainability data. Together with carbon.txt, the schema lays important groundwork for data discoverability, reporting, and transparency
Jan 2025 – Released the first version of our carbon.txt validator service for CSRD reports, extensible code and technical guidance and documentation.
Sept 2024 – Concluded in-depth research and scoping of the technical work required to fetch CSRD and EED data presented in a carbon.txt file.
April 2024 – Awarded funding in NGI Search’s 4th open call to expand the initial prototype to surface more comprehensive sustainability data.
Sept 2023 – Collaborated with Wikirate to understand how much of the internet is covered by credible Net Zero targets. We discovered significant hurdles to collecting sustainability data that we realised extending carbon.txt could overcome.
May 2023 – Ran a closed pilot to prototype a first version of the carbon.txt standard with funding from Internet Society Foundation. We proposed a convention for website owners and digital service providers to demonstrate their digital infrastructure runs on green electricity, which proved successful. Our carbon.txt github repo has more details.
stay updated
Our monthly newsletter is the best way to receive email updates about Green Web Foundation’s work, including carbon.txt. Subscribe to our newsletter.
You can also catch-up on progress via our blog’s dedicated carbon.txt category – https://www.thegreenwebfoundation.org/categories/carbon-txt.
Funding & Financial Support
NGI Search has funded the further development of carbon.txt, including fetching data and releasing the carbon.txt validator service in 2024. The Internet Society Foundation has funded initial research and the first prototype of carbon.txt from 2022-2024. Thank you!