Mixpanel Identify Not Merging Users

How to fix it

Try these in order — the most common fix is first.

1. 1. Use a stable $user_id

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   1. Use a database ID, not an email
   2. Simplified ID Merge cannot merge two $user_ids or change one once set
   3. Check your version in Project Settings > ID Management
   Did this fix it? Yes No

2. 2. Call identify and reset correctly

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   1. Call identify(userId) at signup, login and when the app reopens logged in
   2. Send at least one event afterwards
   3. Call reset() on logout
   Did this fix it? Yes No

3. 3. Fix server-side events

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   1. Generate a UUID per session as $device_id and store it in a cookie
   2. Add $user_id once authenticated and send both on every event
   3. Defer profile updates until the user is identified
   Did this fix it? Yes No

Symptoms

Same person appears as two profiles; pre-login and post-login events are not linked; funnels across login show false drop-offs.

Why it happens

• $user_id changes (for example an email address)
• reset() not called on logout on shared devices
• identify() never called or no event sent afterwards
• Profile properties set on the anonymous ID before the merge are not carried over
• Mapping can take up to 24 hours to reach all reports

This guide also covers

• mixpanel identify not working
• mixpanel duplicate users
• mixpanel alias merge

Other Mixpanel errors

• Mixpanel Events Not Showing
• Mixpanel Not Tracking: Blocked by Ad Blocker
• Mixpanel Data Delay: Events Late in Reports
• Mixpanel Import Failed or Events Dropped
• Mixpanel Event Limit Exceeded and Overage Bill
• Mixpanel Session Replay Not Working
• Mixpanel Users Reset Across Subdomains
• Mixpanel /decide and /flags Requests Failing