Google Analytics (gtag.js) [for multiple UA]
Service marker
<script async src="https://www.googletagmanager.com/gtag/js?id=UA-XXXXXXXX-X"></script>
<script>
window.dataLayer = window.dataLayer || [];
function gtag(){dataLayer.push(arguments);}
gtag('js', new Date());
gtag('config', 'UA-XXXXXXXX-X');
// your optionnal gtag()
</script>