This paper reports a qualitative study that investigates how five different video-based online prototypes impacted in-service music teachers' professional knowledge and their learning experiences. Through an examination of participants' posts and interviews, the findings showed that video-based professional development (PD) could impact teacher's pedagogical content knowledge as they afforded reflections that could change participants' thinking and provided a vicarious experience for music teaching. Situated in a forum, the video-based PD sessions allowed for co-construction of knowledge amongst participants. The findings also revealed challenges in participants' active and sustained participation. The findings are discussed with extant research on effective PD and video-based PD, and take cognisance of heutagogy. We discuss considerations for online video-based PD in terms of PD content design in presenting and exploiting the video material, how we could include the diverse and flexible ways of participation, and the role of the facilitator in providing a safe environment and encouraging multiple perspectives.