Mixpanel Users Reset Across Subdomains

How to fix it

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

1. 1. Use cookie persistence

   Copy steps
   1. Remove persistence: 'localStorage' from init()
   2. Leave cross_subdomain_cookie at its default (true)
   Did this fix it? Yes No

2. 2. Identify at the boundary

   Copy steps
   1. Call identify() on both sites with the same $user_id
   2. Check cookie_expiration (default 365 days)
   Did this fix it? Yes No

Symptoms

Same visitor gets a new ID when moving between www and app subdomains.

Why it happens

• persistence: 'localStorage' is not shared across subdomains
• cross_subdomain_cookie set to false
• Hosting that disallows cross-subdomain cookies

This guide also covers

• mixpanel cross domain tracking
• mixpanel subdomain tracking not working
• mixpanel new distinct id

Other Mixpanel errors

• Mixpanel Events Not Showing
• Mixpanel Not Tracking: Blocked by Ad Blocker
• Mixpanel Identify Not Merging Users
• 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 /decide and /flags Requests Failing