The last decade has witnessed a surge in research into social networks using trace data collected from the Web, triggered by the availability of data on social interactions in social network sites such as Facebook and Twitter and information sharing environments such as newsgroups and blogs. This chapter focuses on the study of these online social networks and on the use of the Web as a rich source of born-digital social data. It begins with an introduction to social networks analysis, outlining the major concepts and how the ‘network perspective’ differs from other social scientific approaches to studying human behaviour. Examples of network research using trace data are provided, which illustrate the methodological approaches and tools available for this type of research. It concludes with some recommendations for researchers who are thinking about using network analysis on how to make best use of the method.