Apdex, an industry open standard for measuring software application performance, calculates a single metric that represents the overall user experience with an app. The Apdex score ranges between 0 and 1, with higher values indicating a more satisfying user experience. It is calculated by bucketing user sessions into four categories: crashing, frustrating, tolerable, and satisfying, based on set targets that can be customized as needed. The overall score is then calculated as the ratio of satisfying and tolerable occurrences to the total number of occurrences. Apdex scores are useful for aligning teams around a specific quality metric and tracking app performance over time, allowing for more holistic views of app quality and customizable thresholds.