The Guidelines for Technology-Based Assessment are the result of a multi-year collaboration by the Association of Test Publishers and the International Test Commission to provide guidance and best practices for the design, delivery, scoring, and use of digital assessments, while ensuring the validity, fairness, accessibility, security, and privacy of such assessments. The document describes the background of, purpose for, and approach to developing the Guidelines, and outlines key related documents and references. In Part II, foundational concepts in measurement are discussed, such as validity, fairness, reliability and the need to manage against threats to measurement that may be introduced in technology-based assessments. Part III contains the guidelines and commentary. Part IV is a discussion of emerging applications of technology in assessment.