HEART stands for Happiness, Engagement , Adoption, Retention and Task Success
Happiness – How much the customers are happy using the product. This is measure of user satisfaction and overall sentiments towards the product. For a mobile app the App Store Reviews are the best measure of users happiness.
Engagement – This refers to the level of involvement of users with the product. This can be measured using the number active users for a app in month. Number of times a particular action was performed by the user.
Adoption – How effectively users are onboarding and using the product. This can be measured by number of new user signups or how many free trial is converted to paid users.
Retention – This refers to the numbers of users retained by the user. This can be measured using the number users retained using a specific period, Churn rate, Customer Life Time Value.
Task Success – This refers to the effectiveness of the product in helping users to complete their tasks. You can measure this by the time taken to complete the task.