I have a question about distinct_id

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The distinct_id is a crucial identifier used by Mixpanel 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 distinct_id value tells Mixpanel which user to attach your events and profile property updates to. It is used to provide a single, unified identifier for a user across devices and sessions. When two events have the same value of distinct_id, they are considered as being performed by one unique user. If the distinct_id on two events are two different values, they will be considered as coming from two separate users[^1^][^2^].In Mixpanel's Ingestion API, distinct_id must be specified on every event, as it is crucial for Mixpanel to perform behavioral analysis (unique users, funnels, retention, cohorts) correctly and efficiently. If the event is not associated with any user, set distinct_id to the empty string. Events with an empty distinct_id will be excluded from all behavioral analysis[^1^].In Mixpanel's Group Analytics, you can establish an event property other than the distinct_id, such as company ID, account ID, project ID, or billing ID, as an identifier by which to analyze your data[^3^].In Mixpanel's Identity API, properties.distinct_id is an optional string that identifies the user post-identification[^4^].In debugging, you can manually trigger some events on your own device and search or filter using distinct_id[^5^].[^1^]: Ingestion API - Events Methods > properties.distinct_id> [^2^]: Identity Management Overview Distinct ID> [^3^]: Group Analytics: Group users together as an aggregated unit of measurement Overview> [^4^]: Create Identity [^5^]: Debugging: Validate your data and troubleshoot your implementation Before You Debug > Find Yourself>

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The $distinct_id_before_identity is an internal Mixpanel property used to track an event's original $distinct_id before it was updated due to identity merging. This property is used in both the Original ID Merge and Simplified ID Merge systems[^1^]. Identity merging is a process in Mixpanel that helps to ensure data are attributed to your users accurately by maintaining ID mappings[^2^]. The $distinct_id_before_identity property helps to keep track of the original distinct ID of a user before this merging process takes place.[^1^]: Reserved Properties: Properties used for system features Reserved Event Properties Part 3> [^2^]: Identity Management Overview

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The distinct_id_before_identity is an internal property used by Mixpanel to track the original distinct_id of an event before it was updated due to identity merging. This property is not directly assigned by the user but is managed by Mixpanel's system[^1^].When a user interacts with an application, Mixpanel's SDK automatically generates a $device_id and assigns it as the distinct_id for the event. This distinct_id is used to track the user's activities as an anonymous user[^2^][^3^].Once the user logs in or signs up, the identify() function is called with the user's known identifier (e.g., their ID from your database), which sets the user_id value. This user_id is then used as the new distinct_id for that user's events moving forward[^2^][^3^][^4^].When both $user_id and $device_id are present in the same event for the first time, Mixpanel creates a mapping to merge these two IDs together, forming an identity cluster[^2^]. This is when the distinct_id_before_identity would reflect the original distinct_id (which was the $device_id) before the identify() function was called.However, the distinct_id_before_identity property is an internal property and its assignment is managed by Mixpanel's system. It's not something that users directly control or assign[^1^].[^1^]: Reserved Properties: Properties used for system features Reserved Event Properties Part 3> [^2^]: Identifying Users (Simplified) Mechanism> [^3^]: Identifying Users (Original) Client-side Identity Management> [^4^]: Identifying Users (Simplified) Server-side Identity Management > Step 3 - Set the Authenticated ID once users log in>

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The identify(user_id) function is used to assign the user_id to the distinct_id for a user's events moving forward. However, there are a few reasons why the user_id might not be assigned to the distinct_id:1. Implementation Issues: There might be an issue with how the identify function is implemented. For example, if a static string is provided for all users instead of the new user ID, all users would actually send events with the same id value[^1^].2. Mixpanel's ID Selection: Mixpanel selects the distinct_id using any of the IDs inside of an identity cluster. This means that even after identifying your user, Mixpanel may choose your user ID or one of the other IDs inside of the cluster (such as the device ID) to serve as the displayed ID for the user. This is random and not user-configurable[^2^].3. Delay in ID Merge Mapping: It may take up to 24 hours for the ID merge mapping to propagate to all other parts of the system. This means that, in some cases, when analyzing a funnel that spans pre-login and post-login behavior in real-time, some may be shown as dropped-off, even though they've performed the conversion event[^2^].If you've identified the problematic set of ID values, but you have not been able to identify the root cause in the implementation, you can reach out to Mixpanel's support team and provide the details you've uncovered so far[^1^].[^1^]: Hot Shard Limits Recovering from a hot shard > Changing your implementation > ID management issue> [^2^]: Identifying Users (Original) FAQ Part 1>

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