# Customer Cohort A **customer cohort** is a group of customers who share a starting characteristic — most commonly the month they signed up — whose behavior is then tracked over time as a single unit. ## Common cohort analyses - **Retention by cohort** — what % of January-2025 signups are still customers 12 months in? - **Expansion by cohort** — how much has the Q1 cohort grown vs the Q3 cohort? - **TTV by cohort** — has time-to-value improved for newer cohorts? - **NRR by cohort** — comparing across acquisition periods ## Why cohort analysis matters Aggregate metrics (total ARR, total customer count) hide trends because they mix old and new customers. Cohort analysis isolates what's happening to *this* group, which reveals whether your motion is improving over time. ## How BlueHill helps Customer records carry signup date and segment tags. Reports can be filtered to compare cohorts (e.g., "Q1 2026 onboarding completions vs Q1 2025"). Related: [Segment](/glossary/segment) · [Lifecycle](/glossary/lifecycle)