Understanding the $device Prefix for User Identifications

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The $device: prefix you're seeing is part of Mixpanel's identity management system, specifically in the Simplified ID Merge approach. Let me explain what this means: In Mixpanel's Simplified ID Merge system, there are two main types of IDs: 1. $user_id - Used for identified users (when they're logged in) 2. $device_id - Used for anonymous users (before they log in)When Mixpanel stores these IDs in an identity cluster, any ID provided as a $device_id is prefixed with $device: in the ID cluster. This helps Mixpanel distinguish between anonymous device IDs and authenticated user IDs within the system.What you're looking at appears to be an identity cluster for a user with the main ID "9af811f2-8e15-4f8a-90c0-2bf670d3ddb9" (without prefix), and multiple device IDs that have been associated with this user over time (all with the $device: prefix).This structure allows Mixpanel to track a user across: - Multiple devices - Before and after login - Across multiple sessionsWhen a user is in an anonymous state, their distinct_id will be set to $device:[device-id]. Once they log in and you call .identify(), Mixpanel will merge the anonymous activity with the authenticated user profile.Identifying Users (Simplified) explains that "Any ID provided as $device_id will be prefixed with $device: in the ID cluster."This approach allows Mixpanel to retroactively merge an unlimited number of anonymous IDs to a single user, ensuring that all user activity is properly attributed regardless of when or where it occurred.

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I need to clarify something important about your question. In the Original ID Merge system, the main ID doesn't actually have a "$device" prefix like you're seeing in the Simplified ID Merge system.In the Original ID Merge system, Mixpanel determines the distinct_id automatically from one of the IDs in the cluster, and it doesn't use the "$device:" prefix convention that's present in the Simplified ID Merge system.According to the documentation: "The distinct_id is automatically determined by Mixpanel using one of the IDs in the cluster and is not user-configurable. Any IDs in the cluster can be used for ingestion." Identity Merge APIsIn Original ID Merge, you would use special events like $identify, $merge, and $create_alias to connect identities, rather than relying on the $device_id and $user_id properties that are used in the Simplified ID Merge system.The "$device:" prefix is specifically a feature of the Simplified ID Merge system, where: - Anonymous IDs are stored with the "$device:" prefix - User IDs are stored without any prefixIf you're seeing "$device:" prefixes in your project, it's likely using the Simplified ID Merge system rather than the Original ID Merge system.Would you like me to explain more about how the Original ID Merge system works compared to the Simplified system?

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Based on the knowledge sources provided, I can explain how Mixpanel handles the $first_name and $last_name properties, but I don't have specific information about Facebook Event Manager's definitions for these fields.In Mixpanel, $first_name and $last_name are reserved profile properties that are used for identifying users. According to the documentation: > "The user's / group's general name, as well as, first and last names. These are primarily useful because they are used, if available, in various Mixpanel UI / reports. For user Cohort Syncs, only $first_name and $last_name is exported." Reserved PropertiesWhen using Mixpanel's Facebook Ads integration for cohort syncing, Mixpanel will send user profile properties including first name and last name to Facebook: > "In order to use this integration, you must set $email as a user profile property or have the advertising ID. In addition to email address, Mixpanel will send a first name user profile property, a last name user profile property, a phone number user property, an advertising id user property and the distinct id." Facebook AdsYour approach of splitting the name field into $first_name (first word) and $last_name (remaining words) is a common implementation pattern, but the knowledge sources don't specifically validate whether this matches Facebook Event Manager's requirements. If you're setting up an integration between Mixpanel and Facebook, I'd recommend checking Facebook's documentation directly to ensure their specific requirements for these fields are met.Would you like more information about how to set up user profiles in Mixpanel or how the Facebook Ads integration works?

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