NumÉcoDiag is a Firefox extension designed to assist French administrations in the ecological digital transition. It features a comprehensive form that incorporates all criteria from the General Reference for the Eco-design of Digital Services (RGESN). Users can evaluate each criterion with four options: To be assessed, Compliant, Non-compliant, and Not applicable. The tool supports sustainable web development by promoting eco-responsibility in digital services.

The extension operates entirely offline, ensuring that no data is collected or transmitted externally, which enhances user privacy. All data is stored locally within the browser, allowing for secure and personal management of information. Additionally, a CSV export function is available, enabling users to easily analyze the results of their assessments. The source code is openly accessible on GitHub, published under a free license, promoting transparency and collaborative development.