Digital discourse has become a widespread way of communicating worldwide, WhatsApp being one of the most popular Instant Messaging tools. This book offers a critical state-of-the-art review of WhatsApp linguistic studies. After evaluating a wide range of sources, seeking to identify relevant works, two major thematic domains were found. On the one hand, references addressing WhatsApp linguistic characteristics: status notifications, multimodal elements such as emojis or memes, language variation, among others. On the other, the volume offers an overview of references describing the use of WhatsApp to learn English as a foreign or second language (EFL/ESL). The author provides a broad critical review of previous works to date, which has enabled her to detect areas of research still unexplored.