Brussels, Belgium, 20th May 2026 – IAB Europe has announced the opening of a public feedback period for carbon.json, a proposed specification designed to enable voluntary, machine-readable disclosure of emissions intensity data by digital advertising systems.
Developed through IAB Europe’s Methodology & Framework Working Group, with input from ad tech companies and sustainability vendors, and in close partnership with Ad Net Zero throughout the development process, carbon.json aims to improve the accuracy and consistency of emissions estimates across the digital advertising supply chain.
The proposed specification enables advertising systems to disclose infrastructure emissions intensity in a standardised, comparable format. These disclosures can then be incorporated into campaign- and path-level emissions calculations by stakeholders across the ecosystem, including DSPs, SSPs, exchanges, ad servers, publisher monetisation platforms, and other intermediaries.
carbon.json has been designed to support organisations operating across a range of infrastructure environments, including public cloud, private cloud, owned data centres, hybrid environments, and managed infrastructure.
The specification is intended to support more accurate and transparent emissions estimation across digital advertising. By making environmental impact metrics available in a structured and machine-readable format, carbon.json can help improve the modelling of supply path emissions and reduce reliance on broad industry averages and default assumptions.
The public feedback process is intended to test the proposed specification with the wider market, identify implementation considerations, and gather input from companies that may publish, consume, validate, or integrate carbon.json disclosures into their own systems and methodologies.
Following the consultation period, IAB Europe intends to address industry feedback and explore the integration of a methodology leveraging carbon.json into the next version of the Global Media Sustainability Framework (GMSF) in partnership with Ad Net Zero. The next version of the GMSF Playbook is due to launch at the end of June 2026.
The proposal is available on IAB Europe’s website here.
The specification is also available on GitHub, including examples for calculating carbon.json disclosures and a JSON schema here.
The related digital advertising emissions methodology is available here.
IAB Europe is inviting stakeholders across the digital advertising ecosystem, including advertisers, agencies, publishers, ad tech companies, sustainability vendors, cloud providers, and measurement and verification providers, to review the proposal and share feedback.
The public feedback period is open until 19th August. Comments and questions can be sent to IAB Europe’s Data & Innovation Strategist, Dimitris Beis, at beis [at] iabeurope.eu.
