Reading retention curves and cohorts in a product case

Define it before you measure it

Retention is the share of a cohort that comes back and does a meaningful action within a time window. Pick the action (not just any event) and the window that matches how often the product is naturally used: daily for messaging, weekly for planning tools.

Read the shape

A curve that flattens means you have a core of retained users. A curve that keeps falling to zero means no habit has formed. A curve that rises later (a smile) usually means resurrected users, which is worth calling out.

Compare cohorts, not averages

A blended retention number mixes old and new users. Split by signup week and by acquisition channel; a drop often traces to one new channel bringing lower-intent users rather than a product problem.

Common mistakes

• Using any event as the return action, which inflates retention.
• Comparing a young cohort's week 1 to an old cohort's week 8.
• Blaming the product before checking a mix shift in acquisition.

Further reading

• Amplitude docs: Interpret your retention analysis
• Amplitude: Mastering Retention playbook