The phenomenon of silence has been investigated in face-to-face learning over the years. It is one of the main concerns in physical classes since it may prevent the quality of teaching and learning and cause a challenge for instructors to negotiate with their students comprehensively. With the advent of technology, online learning has been significant for educators and students, especially during and after the COVID-19 pandemic. In an online learning environment, silence becomes more common than in physical classes and may become a problem in interaction. Hence, this study aims to explore silence in online learning to understand how students experience silence. Fifteen Vietnamese undergraduates were purposefully selected for in-depth interviews using phenomenographic analysis. Two categories were found: low social connectedness and high social connectedness. Students are less involved in social connection, showing their independence and navigation, forming low social connectedness. In contrast, high social connectedness involves more peers and social networks. The findings illustrate the multilayers and complexities of students' silence in an online learning and point out new findings to discover potentially in language learning. It implies that silence is multifaceted and distinguished into non-navigational and navigational online learning conceptions. It implies educators' pedagogical practices in provoking students' attention in online learning and evaluating online presence.