Summary

  • An individual draft dated 28 October 2026 proposes /.well-known/sustainability-data, an HTTPS address where an origin can publish structured energy and carbon declarations for an organisation, service, device or other named target and period.
  • The draft calls every value a self-asserted publisher claim. A signature can establish integrity and continuity of authorship under a trusted key; independent evidence, method and scope determine whether a carbon figure deserves belief.

The easiest part is finding the number

A website can put a small JSON file at a predictable address. A crawler no longer needs to hunt through glossy sustainability pages for a kilowatt-hour figure or a carbon total. That is the useful engineering move in the draft: a fixed HTTPS path, a defined media type and fields for the publisher, target, measurement method, period and methodology. The basic version can be a static file. The operator of the origin writes it. Anyone with access to the origin can retrieve it.

Then the political move begins. A procurement dashboard can copy the field carbon-footprint, display a green tick and quietly promote discoverability into authority. Section 5.1 of the draft prevents that shortcut in its own consumer rules. Every value is a claim of the party publishing the origin’s final response. The file’s presence says what that party chose to publish. It says nothing about the meter behind the number. If the dashboard wants to call a figure verified, its operator needs a separate act of verification. That decision belongs to the consumer, not to the URL.

The declaration’s method field makes the distinction visible. Revision 12 names four routes to a figure: hardware metering, hardware estimation, cloud billing and third-party modelling. A mixed figure carries the least direct method. A methodology link should explain how measurements, estimates, allocations and functional units were chosen. Those fields can expose the seams of an accounting exercise. They cannot make the seams disappear. A service’s share of a shared server may be estimated even when the server’s electricity is metered. A cloud-billing number is a supplier report to its customer.

Put both on the same chart without their methods and the chart has manufactured comparability.

The seal authenticates a pen, not a meter

The optional signed member is a JWS over the declaration object, excluding the signature member itself. The draft requires an asymmetric algorithm and content-type binding. It also makes key choice the consumer’s job. A key offered by the same file is controlled by the same publisher; an independently obtained or previously pinned key can establish more. Even a good signature only establishes integrity and, under some trust arrangements, continuity of authorship. The draft says it does not prove the numeric claim or that the human-readable provider name belongs to the key holder.

That is a precise rebuke to an easy marketing sentence: “Our emissions are cryptographically verified.” Cryptography can tell a reader whether a signed object was altered. It cannot inspect a power meter, choose the correct allocation rule or catch a conveniently narrow boundary. The draft provides links to disclosures and third-party attestations. An attestation counts after a consumer retrieves it, checks its issuer and matches its target and period to the declaration. A blue badge drawn beside a link is merely another drawing.

The upstream field adds a useful confrontation. A hosting or cloud provider can publish a tenant-scoped declaration; the customer can point to it. If the customer’s stated scope covers the supplier’s delivered energy, a customer total lower than that supplier’s comparable figure deserves investigation. The draft does not encode the scope relationship or a per-upstream share, and carbon figures need compatible accounting bases. The comparison is a challenge between two claims, not a universal checksum for the supply chain.

Time matters as much as the signature. A year and its twelve months are two views of the same interval, not thirteen piles to add. Cached responses have a freshness lifetime. A period states when the figure applies. The present tense in a dashboard label can be wrong even when every byte of last year’s signed object is intact. These distinctions are tedious in a press release and decisive in a decision.

Revision 12 is an individual Independent Submission Internet-Draft; its own changelog says the latest edit changed no wire requirement. The work is a proposal for an address and format. The standardisation process has not measured anyone’s emissions. The place to find a number is valuable precisely when the reader remembers who must test it.

Official originals