Definition
Session duration is the time between the start of a visit or app session and the last recorded interaction. It's often averaged across sessions.
Measurement limits
Tools can only measure up to the last recorded event; time spent reading the final page is often lost. Single-page visits may show zero.
Use it carefully
Longer isn't always better: a long session can mean engagement or confusion. In a product, outcomes such as core actions completed say more. On a website, interaction (scrolling, clicking) is a better sign of attention than time alone.