This book pioneers the study of Lánnang-uè, deeply embedded in Manila’s Lannang community’s culture. It approaches Lánnang-uè not just as a language but as a vibrant social practice, highlighting its variability and complex social meanings (e.g., identity-marking). Over six years and with more than 150 participants, the monograph integrates contemporary, community-focused, and critical sociolinguistic frameworks to explore and document linguistic variation as well as change signaling attrition, challenging reductive academic views. Employing diverse methodologies—surveys, elicitation, interviews, computational modeling, and ethnography— the work offers a nuanced depiction of Lánnang-uè’s diversity. A decolonial stance is advocated, emphasizing the complex practices that define the language and its speakers’ identity. It critiques the idea of a uniform linguistic standard, presenting Lánnang-uè as shaped by local, diverse, and inclusive practices, urging a reevaluation of language ownership and authenticity. This monograph is crucial for scholars in sociolinguistics, language variation, and contact linguistics, informing language revitalization efforts and enriching global discussions on linguistic diversity and discrimination.