When I chart my weekly Unique users (iOS native app), grouped by userID I see that ~20% of users each week have a UserID of null.
1. What is UserID? I thought it was Amplitude ID, which should always have a value…
2. Why is it null for ~20% of weekly users?
Notes:
- We use Segment to collect data and stream it through to Amplitude
- We identify all events with a unique system user ID
- We get 1000 new users a week so significantly less than the 1500 above with null userID