You can add analytics tracking scripts, such as those from Google Tag Manager, Facebook, Capture, and others to your Slate branding template.
Scripts in Slate
Slate files requires valid XHTML. In XHTML, attribute minimization is forbidden, and attribute values must always be wrapped in quotes.
📖 W3 Schools - HTML Versus XHTML
Adding scripts to your branding template
Go to Database → Files.
Select Shared.
Select
/shared/build.XSLT.
On any line between the opening
<head>tag and the closing</head>tag, paste the script.
Select Save.