<p>The surge in data traffic across fixed and mobile networks presents critical challenges for reducing greenhouse gas (GHG) emissions in the digital sector. This study analyzes the GHG emissions from internet usage in South Korea, evaluating both technological impacts and rebound effects. Using network-specific traffic data and emission factors (tCO₂eq/TB), we compare emissions before and after 5G deployment. Results show fixed networks (including Wi-Fi) dominate data traffic, while mobile emissions remain elevated due to 4G inefficiencies despite 5G handling most traffic. Our scenario analysis reveals that while 5G’s energy efficiency could theoretically reduce emissions by 61.6%, actual traffic growth diminishes this benefit to 52.6%. Notably, when traffic growth exceeds 150%, the rebound effect fully offsets emission reductions, potentially increasing net GHG output. These findings demonstrate that 5G adoption alone is insufficient for meaningful decarbonization. Instead, achieving carbon neutrality requires an integrated approach combining traffic management, energy-efficient technologies, and renewable energy integration. This study highlights the necessity of addressing both technological efficiency and consumption patterns to mitigate the environmental impact of digital infrastructure. Policymakers and industry stakeholders must prioritize comprehensive strategies to counteract rebound effects and align network growth with climate goals.</p> Graphical Abstract <p></p>