Critical Event
Intermediate PronunciationEN/ˈkrɪtɪkəl ɪˈvɛnt/
A critical event is the action a user has to repeat in a later period in order to count as retained in a retention analysis.
Retention means nothing until the qualifying action is named, and the critical event is that name. An event that is too shallow, such as opening a page, makes almost everyone look retained; one that is too deep, such as completing a purchase, makes a healthy product look dead. Tools word it differently: some call it the return event, others the target action, and some retention reports take two events, one that closes the cohort and one that defines the return. Changing the critical event changes every number on the chart, so a retention figure quoted without its critical event cannot be compared with anything.
FAQ
The action that carries the product's core value and happens often enough to occur inside one reporting period. For a publisher that is reading an article; for a tool it is doing the job the tool exists for. An action that happens once a month will not work on a weekly chart.