# Session Management

A Session represents a continuous period of app usage by a user, and it starts and expires based on specific conditions.

### Session Start Conditions

A session starts under the following conditions by default.

* When the identifier changes
* When an event occurs after the session timeout period has elapsed

### Session Expiration Conditions

When a new session starts, the previous session expires.

* The session expiration time equals the time of the last event.

### Session Policy

The Session Policy is a feature that allows fine-grained control over session persistence and expiration conditions. A Session Policy consists of two types of conditions.

#### Persist Condition

Determines whether to maintain the existing session or start a new one when the identifier changes.

| Option           | Default | Description                                                                                                                                          |
| ---------------- | ------- | ---------------------------------------------------------------------------------------------------------------------------------------------------- |
| alwaysNewSession | default | Always starts a new session when the identifier changes.                                                                                             |
| nullToUserId     |         | Keeps the existing session when userId changes from null to a specific value (i.e., on login). Starts a new session for any other identifier change. |

#### Timeout Condition

Configures the conditions under which a session expires.

| Setting                  | Default               | Description                                                                  |
| ------------------------ | --------------------- | ---------------------------------------------------------------------------- |
| timeout                  | 1800 seconds (30 min) | The session timeout duration.                                                |
| onForeground             | false                 | Whether to check the timeout when an event occurs in the foreground.         |
| onBackground             | true                  | Whether to check the timeout when an event occurs in the background.         |
| onApplicationStateChange | true                  | Checks the timeout when the app state changes (`foreground <-> background`). |

{% hint style="info" %}
For specific configuration code for the Session Policy, refer to the SDK integration documentation for each SDK.
{% endhint %}


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