<p>Hydraulic fracturing is a core stimulation technology for unconventional and low-permeability reservoirs, in which proppants play a critical role in controlling fracture conductivity, effective fracture length, and long-term production performance. This review systematically evaluates current proppant technologies and proposes an engineering-oriented, mechanism-based framework for assessing their performance and field applicability. Proppant behavior is interpreted through three coupled processes: mechanical stability under closure stress, transport and placement efficiency during fracturing, and long-term interaction with fracture surfaces during production. Within this unified framework, conventional and emerging proppant systems, including quartz sand, ceramic, ultra-lightweight, and surface-functionalized proppants, are comparatively analyzed using strength–density relationships and technology maturity–cost matrices. The results show that conventional ceramic proppants provide reliable conductivity under high closure stress but suffer from limited transport efficiency in complex fracture networks. In contrast, low-density and functional proppants enhance placement depth and fracture coverage, often at the expense of mechanical robustness, conductivity retention, or significantly higher volumetric costs. Field evidence reveals a fundamental technological gap: no single proppant system can simultaneously achieve efficient long-distance transport and stable conductivity under high closure stress. Accordingly, hybrid and staged proppant placement strategies are emphasized as a practical solution for full-fracture propping and sustained conductivity. The novelty of this review lies in integrating mechanical, transport, and techno-economic perspectives into a unified evaluation framework.</p>