In his engaging trademark style, Crystal addresses the online linguistic issues that affect us on a daily basis, incorporating real-life examples drawn from his own studies and personal involvement with Internet companies. He provides new linguistic analyses of Twitter, Internet security, and online advertising, explores the evolving multilingual character of the Internet, and offers illuminating observations about a wide range of online behaviour, from spam to exclamation marks. Including many activities and suggestions for further research, this is the essential introduction to a critical new field for students of all levels of English language, linguistics and new media.