Carbon.txt syntax
This page specifies the current v0.6 syntax for carbon.txt files.
Viewing syntax for
Carbon.txt v0.6
| Latest version | Language | Valid from | Valid to |
|---|---|---|---|
| true | TOML | 2026-09-28 | - |
Syntax
| Property | Parent | Type | Required | Description | |||
|---|---|---|---|---|---|---|---|
| version | string | true | carbon.txt syntax version, e.g. "0.6", required from version 0.3 onwards. | ||||
| |||||||
| Property | Parent | Type | Required | Description | |||
|---|---|---|---|---|---|---|---|
| last_updated | date | false | The date this file was last updated, either as a TOML native date (e.g. 2026-10-22), or a string in RFC 3339 format (e.g. "2026-10-22"). | ||||
| |||||||
| Property | Parent | Type | Required | Description | |||
|---|---|---|---|---|---|---|---|
| org | [table] | true | |||||
| ↳ certification_schemes | org | [[array]] | false | Links to certification schemes (such as voluntary standards or ecolabels) which your organization adheres to. Our FAQ has more information on certification schemes. | |||
|   ↳ id | certification_schemes | string | true | A unique ID, used to refer to this certification scheme elsewhere in this carbon.txt. This can be anything you like, as long as it is made up of alphanumeric characters (0-9, a-z, A-Z), hyphens (-) and underscores (_), and it is not already used in this file to refer to another certficiation scheme. | |||
|   ↳ url | certification_schemes | url | true | The URL of the document you are linking to beginning with "http://" or "https://". | |||
|   ↳ title | certification_schemes | string | false | A meaningful title describing the certification scheme. - for instance "B-corporation", "Blauer Engel", or "SCI for Web" | |||
|   ↳ description | certification_schemes | string | false | Any additional information which might be useful to understanding this certification - a brief description of the commitments it represents, or the guarantees it makes. | |||
| |||||||
| Property | Parent | Type | Required | Description | |||
|---|---|---|---|---|---|---|---|
| org | [table] | true | |||||
| ↳ disclosures | org | [[array]] | true | Links to documents that show your organisations sustainability data disclosures. | |||
|   ↳ doc_type | disclosures | string | true | A slugified string representing the type of document you are linking to. Accepted values are: "annual-report", "sustainability-page", "certificate", "csrd-report", "ai-model-card", "measurement-data", "other", or "web-page" (to be deprecated in the next release). See our FAQ for details on each document type. | |||
|   ↳ url | disclosures | url | true | The URL of the document you are linking to beginning with "http://" or "https://". | |||
|   ↳ title | disclosures | string | false | A meaningful title describing the disclosure - for instance "Corporate sustainability report 2026", or "Renewable Energy Certificates covering our energy usage in Q3 2026.". | |||
|   ↳ description | disclosures | string | false | A brief summary of the disclosure, or any additional information needed to understand it. | |||
|   ↳ valid_until | disclosures | date | false | The last date that this disclosure is valid for, if it is time-limited (for example, an annual report or renewable energy certificate), either as a TOML native date (e.g. 2026-10-22), or a string in RFC 3339 format (e.g. "2026-10-22"). | |||
|   ↳ domain | disclosures | string | false | The domain for which the disclosure applies, if this carbon.txt is to be used across multiple domains. This can include any subdomains (e.g. "www."), but should not include the protocol (i.e. "http://" or "https://") or any content paths (e.g "/news/", "/about", "news-update-2025" etc.). | |||
|   ↳ certification_schemes | disclosures | [string] | false | Any certification schemes to which this disclosure relates, Refers to one or more entries in the certification_schemes block of the carbon.txt file, by their ID. | |||
| |||||||
| Property | Parent | Type | Required | Description | |||
|---|---|---|---|---|---|---|---|
| upstream | [table] | false | |||||
| ↳ services | upstream | [[array]] | false | Information linking your organisation to upstream providers you use. | |||
|   ↳ domain | services | string | false | The domain of the organisation providing the upstream service. This can include any subdomains (e.g. "www."), but should not include the protocol (i.e. "http://" or "https://") or any content paths (e.g "/news/", "/about", "news-update-2025" etc.). | |||
|   ↳ service_type | services | string or ["array of strings"] | false | A slug representing the service provided by the upstream provider. | |||
| |||||||
Code sample
version="0.6"
last_updated=2026-10-22
[org]
certification_schemes = [
{ id = "blauer-engel",
url = "https://www.blauer-engel.de/en/productworld/software",
title = "Blauer Engel Resource and Energy-Efficient Software Products",
description = "The aim of the environmental label for resource and energy-efficient software products is to reduce the total energy consumed by information and communication technology and improve resource efficiency."
},
]
disclosures = [
{ doc_type = "web-page", url = "https://mycompany.com/sustainability", domain = "mycompany.com", certification_schemes=["blauer-engel"], description="This company's sustainability policy." },
{ doc_type = "annual-report", url = "https://mycompany.com/carbon-emissions-2025.pdf", valid_until = 2025-12-31, title = "Emissions Report 2025" },
{ doc_type = "measurement-data", url = "https://mycompany.com/dist.json", title = "Quarterly emissions figures", description = "Estimated carbon impact data for this company's digital operations, in DIST format" }
]
[upstream]
services = [
{ domain = "cloud.google.com", service_type = "shared-hosting" },
{ domain = "aws.amazon.com" }
]