## 1 Introduction  
With increasing popularity, social media (e.g., virtual communities, weblogs, wiki, and social networking sites) has become a useful channel for socializing [1; 2; 3]. It enables people to create and maintain their social networks regardless of the limitation of geographic location [4; 5]. People build their online social networks to satisfy their needs for social support [1]. Online social support could help social media users to solve their problems, effectively manage stress, and mitigate the impact of negative life events [6]. As such, the proper use of social media can enhance users' quality of life and facilitate subjective well-being [1; 7]. Subjective well-being is a key factor that maintains users' continuance intention toward information technologies, including social media [8]. Understanding the effect of social media use on subjective well-being has become increasingly critical in information systems (IS) research. Existing studies have examined the link between social capital and subjective well-being [7; 8], as well as the influence of receiving social support on one's quality of life [9]. These studies have provided valuable insights into the nature of social capital; close connections with others allows users to obtain information and support from others [7; 10]. Furthermore, receiving online support from others may facilitate one's subjective well-being [7]. In this sense, social support may mediate the relationship between social capital and subjective well-being. However, only a few studies have explored the relationships among social capital, online social support, and subjective well-being on social media. Online support generally involves two distinct types of activity: seeking online support and providing online support [11]. Little attention has been paid to the effects of various types of online social support on users' perceptions of well-being. In addition, the perception of well-being derived from social media use reflects one's subjective evaluations of his/her cognition and perception of social media use at a static point [7; 12]. In fact, an individual's cognition and perception may change when his/her experience of information technology usage increases over time [13]. Therefore, the influence of online support activities on subjective well-being may vary as one's use experience increases. To the best of our knowledge, few studies have been carried out to explore the moderating role of experience on the link between subjective well-being and online social support. To address this research gap, we developed a research model by integrating the perspectives of social capital theory, social support, and experience. Based on the assertions of previous the literature [11; 14], we hypothesize that social support on social media can be divided into two different types: receiving online support and providing online support. We then argue that the two types of social support can enhance subjective well-being, based on the previous literature on social support (e.g., [11; 15; 16]). We also propose that social capital impacts these two types of social support, based on the standpoint of [14], that people with higher levels of social relationship are more likely to get help from others and help others in a social unit. Additionally, we employ experience as a moderator in the model. We propose that providing online support exerts a stronger effect on the subjective well-being of users with less experience, while receiving online support will have a greater impact on the subjective well-being of users with more experience. This study contributes to social media research in two ways. First, we demonstrate that social capital does increase the development of online support activities, which in turn enhances users' subjective well-being. Second, by applying the viewpoint of experience, we further illustrate how experience of social media usage impacts the relationship between social support and subjective well-being. This paper is organized as follows.