Objective: To quality assess a sample of health behavior change apps from the NHS Apps Library using a rating tool based on the 2014 National Institute for Health and Care Excellence behavior change guidance (NICE BCG). Methods: A qualitative analysis of the NICE BCG identified themes and questions for a quality assessment of health behavior change apps. These were refined by further discussion and piloting, and applied by two independent raters to a sample of NHS Library apps (N=49). Disagreements were resolved following discussions with a third rater. Results: Themes identified were; purpose, planning, usability, tailoring, behavior change technique (BCT), maintenance, evaluation, data security and documentation. Overall, purpose of the...