Forward conversion data to a self-hosted Matomo through sGTM

If you run Matomo alongside or instead of GA4, your sGTM container can forward events to Matomo using its tracking API.

Map GA4 events to Matomo

GA4	Matomo
page_view	action_name
purchase	idgoal=0, ec_id, revenue
add_to_cart	e_c=Ecommerce, e_a=AddToCart

A Custom Tag in sGTM

const params = {
  idsite: data.siteId, rec: 1,
  url: getEventData('page_location'),
  action_name: getEventData('page_title')
};
if (data.eventName === 'purchase') {
  params.idgoal = 0;
  params.ec_id = getEventData('transaction_id');
  params.revenue = getEventData('value');
}
sendHttpRequest('https://matomo.example.com/matomo.php?' + encodeUriParameters(params));

Matomo uses _id for visitor identification. Generate per-user and store in a first-party HttpOnly cookie.