In this paper the results of an online survey (n=210) regarding the usefulness of Facebook for informal L2 learning will be presented. Participants were individual Facebook users who study either German (n=118) or Japanese (n=92). By using a combination of open and closed questions, the mostly quantitative findings of the survey indicate that for most participants Facebook is a suitable tool for improving their L2 skills, because the network enables them to establish or to maintain social contacts with native speakers and to have authentic opportunities to express themselves in the L2. As particularly effective activities, participants mentioned reading and writing L2 posts on the networks' timeline, exchanging private messages, and commenting on friends' posts. As far as effects on L2 learning are concerned, most participants noted an improvement in their reading and writing skills, as well as an expansion of their vocabulary and cultural understanding. Some respondents, however, raised concerns about the formal correctness of the language they encounter on the network as well as insecurity regarding communication with strangers. The information participants provided on their informal use of Facebook led to the conclusion, that learners of L2 German and learners of L2 Japanese show similar tendencies in using the network for their L2 learning. In contrast to using social networks in educational settings, their informal use allows learners much more freedom to decide when, how often, with whom, on which topic, and in which way they wish to interact in their target language on the network.