This Recommendation provides specific principles and requirements for evaluating the carbon footprint of smartphones. In the context of environmental impact assessment where continuous improvements are searched, this Recommendation aims to improve the accuracy, consistency and transparency of carbon footprint assessments results for such products. The Recommendation establishes a guideline tailored to smartphones, including guidance on handling smartphone‑specific aspects such as the contribution of key components, the modelling of use‑phase electricity consumption, the transport of globally sourced parts, and end‑of‑life treatment. It is intended to help stakeholders comprehensively understand the carbon emissions across the entire smartphone life cycle and to identify key mitigation strategies, from design and material selection to software optimization and circular economy practices. The work will consider relevant existing frameworks such as ITU-T L.1400-series of Recommendations (in particular ITU-T L.1410), ISO 14067, and the Eco-rating initiative on smartphones, to ensure consistency with these frameworks.