Understanding Distinct ID, User ID, and Identify Events

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In Mixpanel, distinct_id, $user_id, and identify events are key components of identity management that help track users across sessions and devices. Here's an explanation of their differences:

The distinct_id is Mixpanel's core identifier used to uniquely track users in the system: - It's the primary property that determines user uniqueness in Mixpanel - When two events have the same distinct_id, they're considered as performed by the same user - It's essential for features like Insights reports (for unique user counts), Funnels (tracking conversion journeys), and User profiles - For profile updates, it's referenced as $distinct_id instead of distinct_idIdentity Management Overview explains: "Distinct ID is Mixpanel's identifier used to uniquely track a user in the system. Every event data and profile update sent to Mixpanel should have a distinct_id property associated with it."

The $user_id is a specific event property that represents an authenticated user: - It's typically set when a user logs in or signs up - In Simplified ID Merge (newer system), when an event contains a $user_id, that value becomes the distinct_id for the event - It represents the known identifier for a user (like a database ID) - When both $user_id and $device_id appear in the same event, Mixpanel creates an identity mapping between themIdentifying Users (Simplified) states: "Calling identify(<user_id> ) sets the user_id value passed to the identify function as the $user_id event property for the user's events moving forward."

Identify events are mechanisms to link anonymous users to known users: - In Original ID Merge: The $identify event is a special event type used to link an Anonymous ID and your chosen User ID - It's triggered when you call .identify(<user_id> ) using Mixpanel's SDKs - In Simplified ID Merge: No special event is needed - just including both $device_id and $user_id properties in the same event creates the mapping - This process allows Mixpanel to stitch together pre-login and post-login behaviorIdentifying Users (Original) explains: "The $identify event is used to link an Anonymous ID and your chosen User ID together."

Mixpanel has two ID merge systems with different approaches: Simplified ID Merge (newer): - Uses $device_id and $user_id properties directly on events - The $user_id always becomes the distinct_id - No limit on how many $device_ids can be merged to a single $user_idOriginal ID Merge (older): - Uses special events ($identify, $merge, $create_alias) to manage identities - The distinct_id is automatically determined by Mixpanel from the ID cluster - Limited to 500 IDs per clusterUnderstanding these differences is crucial for properly implementing user tracking in Mixpanel and ensuring accurate analytics across user sessions and devices.

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