This volume presents the second edition of the Communicative Orientation of Language Teaching (COLT) Observation Scheme. Since the book’s original publication, COLT has become well established as a research instrument in L2 teaching and learning. This new edition brings COLT into the 21st century by introducing digital versions of the scheme and describing how advances in technology have made the collection, coding, analysis, and synthesis of classroom data faster and more efficient. Enhancements include the availability of web-based platforms for the coding, sharing and storage of data, the application of artificial intelligence in the coding of classroom observation data, numeric coding systems, and ongoing work in the use of automatic speech recognition for faster transcription. The volume has a similar organizational structure to the original COLT book with the addition of a new chapter on Digital COLT (Part A), a new section on Numeric COLT (Part B), and an expanded final chapter that includes updated summaries reporting on the use of COLT for a wide range of research purposes in diverse L2 contexts. As with the first edition, the material is presented in a user-friendly manner with examples, illustrations and hands-on activities throughout. It is intended for both novice and experienced researchers investigating teaching and learning in L2 classrooms and in teacher education/reflective practice research.