Linking First Time App Opens to User ID After Registration

Sikandar S. · 2025-07-30T12:32:32.545Z

I’m facing an issue: when a new user opens the app for the first time, an event called *"First Time App Opened"* is sent to Mixpanel. However, at that point, no user ID is attached to the event. The `identify()` function is only called after the user completes registration, which means there's no way to link the *first-time open event* with the rest of the user's session or activity. I’m looking for a way to associate that initial event with the same user after they've registered.

Linking First Time App Opens to User ID After Registration | Mixpanel Community

6 comments

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kapa.ai
APP
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Please stand by Sikandar S. as I search the knowledge base. I normally take about 15 seconds or so. 👋
Feel free to ask a follow-up question once I've answered by mentioning me with @kapa.ai
kapa.ai
APP
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You can solve this issue by leveraging Mixpanel’s identity management and ID Merge system. Here’s how it works and what you should do:
How Mixpanel Handles Anonymous and Identified Events
When a new user opens your app for the first time, Mixpanel’s SDK automatically assigns a unique anonymous identifier called $device_id to that user. All events (including your "First Time App Opened") are tracked with this $device_id as the distinct_id until you call identify() with a known user ID after registration or login.Key Point: When you later call identify(<user_id> ) after registration, Mixpanel merges the anonymous $device_id with the new $user_id. This means all events previously tracked with the $device_id (including the initial app open) are retroactively associated with the user’s profile. This process is called ID Merge and ensures a unified user journey, linking pre-registration and post-registration events together automatically Identifying Users (Simplified).
What You Should Do
- Do not call identify() for anonymous users. Let Mixpanel assign and use the $device_id for all pre-registration events. - Call identify(<user_id> ) immediately after registration or login. This will merge the anonymous and identified states. - No need to manually attach the user ID to the initial event. Mixpanel will handle the retroactive association for you.Example Flow:Result: The "First Time App Opened" event and all subsequent events are linked to the same user profile once the user registers Understanding Simplified ID Merge Example User Flows.---Summary: You do not need to change your current approach. As long as you call identify() with the user ID after registration, Mixpanel will automatically associate the initial anonymous events (like "First Time App Opened") with the registered user’s profile.If you have further questions about edge cases or want to confirm your project’s ID Merge API version, check your project settings as described in the documentation Identifying Users (Simplified).
kapa.ai is still learning and improving, please let me know how I did by reacting below.
ℹ️ Tip: Mention @kapa.ai in the thread for follow-ups or DM the app for 1-to-1 help.
Sikandar S.
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Sultan A. we have implemented this approach as suggested by bot already.
Sultan A.
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The problem is the events are still not linked with the same user profile yet, Sikandar S. you can see the evidence on the ticket
Sikandar S.
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Sultan A. we can go through our implementation again, just to confirm.
Sultan A.
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Sikandar S. sure

kapa.ai
APP
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·
Please stand by Sikandar S. as I search the knowledge base. I normally take about 15 seconds or so. 👋
Feel free to ask a follow-up question once I've answered by mentioning me with @kapa.ai
kapa.ai
APP
·
·
You can solve this issue by leveraging Mixpanel’s identity management and ID Merge system. Here’s how it works and what you should do:
How Mixpanel Handles Anonymous and Identified Events
When a new user opens your app for the first time, Mixpanel’s SDK automatically assigns a unique anonymous identifier called $device_id to that user. All events (including your "First Time App Opened") are tracked with this $device_id as the distinct_id until you call identify() with a known user ID after registration or login.Key Point: When you later call identify(<user_id> ) after registration, Mixpanel merges the anonymous $device_id with the new $user_id. This means all events previously tracked with the $device_id (including the initial app open) are retroactively associated with the user’s profile. This process is called ID Merge and ensures a unified user journey, linking pre-registration and post-registration events together automatically Identifying Users (Simplified).
What You Should Do
- Do not call identify() for anonymous users. Let Mixpanel assign and use the $device_id for all pre-registration events. - Call identify(<user_id> ) immediately after registration or login. This will merge the anonymous and identified states. - No need to manually attach the user ID to the initial event. Mixpanel will handle the retroactive association for you.Example Flow:Result: The "First Time App Opened" event and all subsequent events are linked to the same user profile once the user registers Understanding Simplified ID Merge Example User Flows.---Summary: You do not need to change your current approach. As long as you call identify() with the user ID after registration, Mixpanel will automatically associate the initial anonymous events (like "First Time App Opened") with the registered user’s profile.If you have further questions about edge cases or want to confirm your project’s ID Merge API version, check your project settings as described in the documentation Identifying Users (Simplified).
kapa.ai is still learning and improving, please let me know how I did by reacting below.
ℹ️ Tip: Mention @kapa.ai in the thread for follow-ups or DM the app for 1-to-1 help.
Sikandar S.
·
·
Sultan A. we have implemented this approach as suggested by bot already.
Sultan A.
·
·
The problem is the events are still not linked with the same user profile yet, Sikandar S. you can see the evidence on the ticket
Sikandar S.
·
·
Sultan A. we can go through our implementation again, just to confirm.
Sultan A.
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·
Sikandar S. sure

6 comments

How Mixpanel Handles Anonymous and Identified Events

What You Should Do

How Mixpanel Handles Anonymous and Identified Events

What You Should Do