A cohort is a group of contacts who share a defining event in the same time window — most often the month they subscribed — tracked together over time to see how their behaviour evolves.
In depth
Cohort analysis reveals trends that whole-list averages hide. By following each signup month separately you can see whether newer subscribers engage better or worse than older ones, and exactly when a cohort’s engagement starts to decay.
Example
Your January cohort still opens at 30% after six months, but your April cohort dropped to 15% in three. That gap points to something that changed in April — a bad lead source or a weaker welcome flow — which a blended open rate would never surface.
Related terms
See how engagement decays over time in our email marketing guide.