@dariusz_wieckiewicz Do you send first_visit / session_start events as well? Officially they are reserved / not supported via MP, but you can send them using "region1.analytics.google.com/g/collect URL".

BTW, a sidenote - localStorage requires standard GDPR consent as well when used for analytics/marketing purposes.

@dusoft first visit and session start, yes.
@dariusz_wieckiewicz but do you send it via this "hack" url or via MP?
@dusoft it’s not a hack, it official way how GA4 sending a trigger. Not also pure MP, but rather something in a middle. BTW this feature was on since day one before MP was even mentioned.
@dariusz_wieckiewicz i know but it's not documented as way to send backend events 😁