Incorrect user recognition (Too many actions associated with the same user)

Hello everyone and thanks you for your support :slight_smile:

We (a website with around 2 millions visites by month) recently switch from GA4 to Matomo.

And I discovered that our implementation of Matomo does not separate well the different users and too many different actions are associated to the same users, when I am convinced that they are different users.

Indeed, several findings corroborate this observation:

  • In several analyzed visits, there are inconsistent action sequences (user creating an account 2 minutes after logging in).
  • Most of our Android users are visiting on several different phones (while we do not send any internal ID to Matomo to recognize them across devices).
  • Our number of visitors and sessions has decreased by 2 thirds while the number of page views and events remains constant.
  • The number of visite by user increased a lot.
  • Our engagement time has largely increased, without any change in the site.

We use _pk_id cookie to identify visitor and we don’t transmit any internal userId to recognize users across devices.

Have you ever encountered this problem on sites with a lot of traffic? Are there any pitfalls to avoid in the Matomo configuration that could cause this?

Thanks you for your help.