Social media has become a central infrastructure for brand communication in the contemporary digital environment. However, the progressive maturation of the social media ecosystem -characterized by content saturation, algorithmic sophistication, and intensified competition for attention- has substantially transformed the dynamics of interaction between brands and users. This study provides a longitudinal analysis of brand performance on social media in Spain during the 2024-2025 period. The research adopts a quantitative, descriptive, and longitudinal approach, based on secondary analysis of aggregated data from a sample of 196 brands across various economic sectors with active presence on major social platforms. The results reveal sustained growth in brands’ digital communities, accompanied by a significant reduction in both publication volume and average interactions, confirming a structural decline in organic reach. Moreover, notable differences emerge by sector and platform, alongside the growing centrality of communication efficiency as a strategic indicator in a context increasingly focused on resource optimization.