Closed-loop supply chains (CLSCs) are an important response to pressing sustainability challenges. However, they bring about tradeoffs like increased resource use in logistics. Addressing these complexities, digital platforms emerge as promising, yet under-researched, tools for efficiency enhancement in CLSCs. This study investigates three digital platforms facilitating furniture and household item trade in relation to CLSCs. A comprehensive framework, rooted in literature on CLSCs, digital platforms, and logistics, guides the analysis. The findings reveal diverse sustainability potentials within these platforms, primarily driven by system design, scale, and actor engagement. The efficacy of the digital platform varies based on usage patterns, their geographical scope, logistic solutions, and providers. Crucially, environmental and social sustainability tradeoffs and benefits come to light, offering insights into their emergence based on system design. This study provides insights for practitioners and scholars, regarding potentials/risks of trade-offs in environmental and social sustainability dimensions related to the use of digital platforms for trading secondhand furniture. It provides a nuanced understanding of how these differ depending on system design.