Sessions Per User (SPU)
How often users return to your product in a given period.
SPU = Total sessions / Total unique users
What it measures
Average number of separate sessions per user over a given period. A session typically ends after 30 minutes of inactivity, though this varies by platform.
What to watch
- Rising: Users are returning more frequently, a sign of habit formation. High-frequency products (messaging, social) should target 3+ daily sessions; lower-frequency products (finance, travel) may see 2-4 weekly.
- Falling: Users may be consolidating activity into fewer, longer sessions (not necessarily bad) or losing interest. Cross-reference with session duration to distinguish these cases.
In practice
A news app saw SPU rise from 1.4 to 2.1 after launching personalized feeds, but average session duration dropped 30%. Users were snacking on headlines rather than reading articles. The team added a "deep read" mode and saw both metrics improve together.
Related: DAU — frequency without depth can be hollow.; DAU/MAU Stickiness — measures habit strength across a month.