# Session timeout

> How long a visitor can be inactive before their session ends and the next action starts a new one.

Source: https://datacenter.so/glossary/session-timeout
Also called: session timeout duration, inactivity timeout.

A [session](https://datacenter.so/glossary/session) has no natural end; the visitor just stops. So tools pick a rule. In GA4, a session ends after 30 minutes without activity by default, and there is no limit on how long an active session can last. You can change the web timeout per data stream under **Configure tag settings**, **Adjust session timeout** ([Google](https://support.google.com/analytics/answer/9191807)).

The timeout changes the counts. A shorter timeout splits one long visit into several sessions; a longer one merges them. A reader who leaves a tab open over lunch and comes back starts a second session in GA4, often with landing page (not set), because no page loaded. See [GA4 (not set)](https://datacenter.so/guides/ga4-not-set).

Not every tool uses a timeout. Datacenter counts a visit as one visitor's day on a site, so its visits are longer and fewer than GA4 sessions. See [sessions, users and pageviews](https://datacenter.so/guides/sessions-users-pageviews).

## Related terms

- https://datacenter.so/glossary/session
- https://datacenter.so/glossary/unique-visitor
- https://datacenter.so/glossary/engagement-rate