Formula
Users active on Day 30 / Total new signups x 100
How to measure
Track a signup cohort and measure the percentage who trigger an active-use event around day 30 after signup.
Why track it
D30 retention is a strong proxy for whether a product has found a repeatable habit or use case beyond the initial novelty period.
Example
A team treats 30% D30 retention as its internal benchmark for a cohort that has genuinely adopted the product.