# Session Tracking in RudderStack SDKs


This guide explains the session tracking feature in RudderStack.

## Overview

RudderStack provides a **session tracking** feature that helps you track user sessions and gather event tracking metrics. You can use this feature to:

- Combine events with session metadata to better understand the user's product journey and analyze their behavior.
- Use the insights to identify problems and optimization opportunities in your product workflow.

#### What is a session?

A session is a group of user interactions with your website or mobile app within a given time frame. It is usually triggered when a user opens a mobile app or a website in their browser and ends after a particular period of inactivity.

{{< info >}}
A single session can contain multiple page views or screen views, events, social interactions, and ecommerce transactions.
{{< /info >}}

## Session tracking in RudderStack SDKs

The following RudderStack SDKs support the session tracking feature:

| RudderStack SDK | Minimum supported version |
| :---- | :---- |
| [JavaScript]({{< ref "sources/event-streams/sdks/rudderstack-javascript-sdk/_index.md" >}}) | <ul><li>v1: **1.16.0** (CDN)</li><li>v1.1: **2.15.0** (CDN & NPM)</li></ul> |
| [Android (Java)]({{< ref "sources/event-streams/sdks/rudderstack-android-sdk/_index.md" >}}) | **v1.7.0** |
| [iOS (Obj-C)]({{< ref "sources/event-streams/sdks/rudderstack-ios-sdk/_index.md" >}}) | <ul><li>[v1]({{< ref "sources/event-streams/sdks/rudderstack-ios-sdk/_index.md" >}}): **v1.7.0**</li><li>[v2]({{< ref "sources/event-streams/sdks/rudderstack-ios-sdk/ios-v2.md" >}}): **v2.3.0**</li></ul> |
| [React Native]({{< ref "sources/event-streams/sdks/rudderstack-react-native-sdk.md" >}}) | **v1.8.0** |
| [Flutter]({{< ref "sources/event-streams/sdks/rudderstack-flutter-sdk/_index.md" >}})  | **v2.7.0** | 

You can expect the following properties in your event's [context object]({{< ref "event-spec/standard-events/common-fields.md#contextual-fields" >}}) object when session tracking is enabled:

| Property | Type | Description |
| :---- | :---- | :---- |
| `sessionId` | Number | The session ID. <br /><br />See the [FAQ]({{< ref "sources/event-streams/sdks/session-tracking/faq.md#how-does-rudderstack-determine-the-session-id" >}}) guide for more information on how RudderStack calculates `sessionId` . |
| `sessionStart` | Boolean | Present in the first event, indicating the start of the session. |

{{< warning >}}
Note the following:

- RudderStack's [automatic session tracking]({{< ref "sources/event-streams/sdks/session-tracking/automatic-session-tracking/" >}}) feature overrides any `sessionId` present in the event's `context` object.
- Make sure to send any other session-related information within the event's `traits` or `properties` object.
{{< /warning >}}

## Session tracking types

The RudderStack SDKs mentioned above support two types of session tracking:

| Type | Description |
| :---- | :---- |
| [Automatic session tracking]({{< ref "sources/event-streams/sdks/session-tracking/automatic-session-tracking/" >}}) | RudderStack automatically determines the start and end of a session based on the inactivity time configured in the SDK. |
| [Manual session tracking]({{< ref "sources/event-streams/sdks/session-tracking/manual-session-tracking.md" >}}) | You can manually start and end a session using the SDK methods. |

## Supported downstream tools

The RudderStack SDKs support sending the `sessionId` and `sessionStart` fields to all [cloud]({{< ref "destinations/streaming-destinations/_index.md" >}}) and [warehouse]({{< ref "destinations/warehouse-destinations/_index.md" >}}) destinations, **within the event's `context`**.

It is important to note the following:
- RudderStack passes the `sessionId` to the subsequent events in the `context.sessionId` field.
- RudderStack sets the `context.sessionStart` field to `true` in the first event to indicate the start of the session.

RudderStack maps `sessionId` to specific fields **only** in case of the following two destinations:

| Destination       | Notes          |
|-------------------|-------------|
| [Amplitude]({{< ref "destinations/streaming-destinations/amplitude/" >}}) | RudderStack maps `sessionId` to Amplitue's `session_id` field. For more information, see the [Amplitude documentation](https://www.docs.developers.amplitude.com/analytics/apis/http-v2-api/#keys-for-the-event-argument:~:text=to%20occur%20simultaneously.-,session_id,-Optional.%20Long.%20The"). |
| [Mixpanel]({{< ref "destinations/streaming-destinations/mixpanel/" >}}) | <li>RudderStack passes the `$session_id` under the event properties.</li> <br/> <li>Mixpanel doesn't have a specific field for `$session_id` but you can use this field in the reports.</li> |

## FAQ

See the [Session Tracking FAQ]({{< ref "sources/event-streams/sdks/session-tracking/faq.md" >}}) guide for answers to some commonly-asked questions on session tracking.

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