Session timeout customization
A session ends after a period of inactivity, and that timeout is configurable. Lengthen it and long pauses no longer split a visit into two sessions; shorten it and they do. Either change moves session counts, sessions-per-user, and engagement, and it makes your data diverge from any tool on a different timeout. This page explains how customising the session timeout reshapes metrics.
What the timeout controls
Analytics groups a visitor's events into a session and closes the session after a configured period without activity — 30 minutes by default in GA4, adjustable within allowed bounds. A gap longer than the timeout starts a new session on the next event, so the timeout directly sets how a single visit with pauses is divided.
Raise the timeout and fewer sessions form from the same behaviour; lower it and more do.
- Sessions close after a configurable inactivity gap
- GA4 default is 30 minutes, adjustable within limits
- The timeout sets how pauses split a visit
Effects on metrics and comparisons
Because session count is a denominator for many metrics, changing the timeout moves sessions-per-user, pages-per-session, and engagement rate even when underlying behaviour is identical. A change creates a seam in trend lines on the date it took effect, since history is not reprocessed.
Two tools with different timeouts will not agree on session counts. When comparing, align timeouts where you can and treat a timeout change as a reason for a step, not a real shift.
How it appears in analytics and logs
A step change in session counts or sessions-per-user with no traffic change often coincides with a session-timeout setting being altered.
Diagnostic use case
Understand how a custom session timeout changes session counts and engagement, and account for it when comparing periods or tools.
What WebmasterID can help detect
WebmasterID records raw event timing, so you can reason about sessionisation directly rather than being locked to one tool's timeout window.
Common mistakes
- Changing the timeout mid-analysis and ignoring the seam.
- Comparing session counts across tools on different timeouts.
- Reading a timeout-driven step as a behaviour change.
Privacy and accuracy notes
Session timeout is a measurement setting based on inactivity, not on visitor identity. It carries no privacy implication.
Related pages
- Session fragmentation and inflation
A session is meant to represent one continuous visit, but several rules can split one journey into many. A timeout during a pause, a campaign parameter mid-visit, crossing midnight, or a self-referral each starts a fresh session. The result inflates session counts and shrinks per-session metrics. This page explains the fragmentation rules and how to read counts affected by them.
- Campaign timeout window effects
A campaign or acquisition timeout controls how long the source that brought a visitor keeps getting credit for their later sessions. When that window expires before the visitor returns, the next session is no longer attributed to the original source and often falls to Direct. Changing the window moves attribution between channels. This page explains the campaign timeout and its effect on source reports.
- GA4 session redefinition gaps
GA4 redefined the session. Instead of Universal Analytics' rules that broke a session at midnight and on each new campaign source, GA4 starts a session with a session_start event, keeps it alive within a timeout window (default 30 minutes), and does not split it on a new campaign or at midnight. Teams migrating from UA see session counts and per-session metrics shift because of this redefinition.
- Web analytics
Reason about sessionisation from raw event timing.
Sources and verification notes
Last reviewed 2026-06-24. Facts are checked against primary/official sources where available; uncertain specifics are marked “Data not yet verified” rather than guessed.