GA4 and Piwik data discrepancies


We’ve got both GA4 and Piwik installed. much prefer piwik but we’ve noticed that the data counts of both systems despite both been set to fire post consent are different. Here is an example of user counts over the same period of time:


I presume they should match, or if not match, at least be similar. Can anyone shed some light on what may be causing this massive difference in user counts?

edit: i should add i have tested the tag firing on various random pages and both tags are firing and show in the debugger.



Hi there!

In general comparing data using different tools will always lead to certain deviations. Each tool runs on an independent engine to process the data and also uses a different approximation algorithm.

Simultaneously there is no strict answer to what might cause such deviation between Google Analytics and Piwik PRO data. Too many various factors can cause such behavior which is impossible to pinpoint.

Here is an article that might help you identify where data discrepancies can come from: