In the digital era, social media is no longer a peripheral tool but the beating heart of library outreach— a dynamic circulatory system delivering knowledge across digital terrains. This study systematically investigates how libraries strategically deploy social media platforms to market services, engage users, and overcome institutional constraints. Using a structured literature review of 24 peer-reviewed empirical studies published between 2012 and 2025, this article applies the PRISMA 2020 reporting guidelines and the SPIDER framework to ensure methodological transparency and relevance to information science contexts. The analysis reveals six dominant thematic categories: study characteristics, platform usage patterns, strategy techniques, engagement metrics, institutional challenges, and cross-study thematic convergence. Facebook and Instagram emerged as the most utilized platforms, with academic libraries favoring visual content and public libraries emphasizing event-driven interaction. Libraries employed storytelling, scheduling, and hashtag campaigns to enhance visibility, while engagement metrics—likes, shares, and direct messages—provided feedback loops for optimizing digital strategies. However, significant challenges persist, including staffing limitations, policy bottlenecks, and algorithmic opacity that restrict organic reach. The thematic synthesis identifies three integrative insights: the need for platform–purpose alignment, the effectiveness of analytics-informed strategies, and structural barriers to scalability. This review offers a multidimensional perspective on the evolving role of social media in library marketing, contributing both conceptual clarity and practical guidance for institutions seeking to enhance digital engagement. The findings serve as a roadmap for future empirical research and digital transformation initiatives in both academic and public library systems.
