Support Google Tag Manager approach to analytics

yndajas · yndajas · commit 04717903fd95 · 2025-11-14T14:45:03.000Z
We already support the other approach to tracking data for Google Analytics 4: gtag.js. We need to support the Google Tag Manager approach to address new needs https://support.google.com/tagmanager/answer/7582054 https://developers.google.com/tag-platform/tag-manager/datalayer
diff --git a/example/config/tech-docs.yml b/example/config/tech-docs.yml
@@ -22,6 +22,8 @@ footer_links:
 # Tracking IDs
 # Google Analytics 4 using gtag.js (e.g G-XXXXXX)
 ga4_tracking_id:
+# Google Analytics 4 using Google Tag Manager (e.g GTM-XXXXXXXX)
+ga4_gtm_tracking_id:
 # Google Universal Analytics (e.g. UA-XXXX-Y)
 ga_tracking_id:
 
diff --git a/lib/source/layouts/_analytics_ga4_gtm.erb b/lib/source/layouts/_analytics_ga4_gtm.erb
@@ -0,0 +1,9 @@
+<% if config[:tech_docs][:ga4_gtm_tracking_id].is_a?(String) && !config[:tech_docs][:ga4_gtm_tracking_id].empty? %>
+  <!-- Google Tag Manager -->
+  <script>(function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':
+  new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],
+  j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src=
+  'https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);
+  })(window,document,'script','dataLayer','<%= config[:tech_docs][:ga4_gtm_tracking_id] %>');</script>
+  <!-- End Google Tag Manager -->
+<% end %>
diff --git a/lib/source/layouts/core.erb b/lib/source/layouts/core.erb
@@ -2,6 +2,7 @@
 <html lang="en" class="govuk-template <%= config[:tech_docs][:show_govuk_logo] ? 'govuk-template--rebranded ' : '' %>no-js">
   <head>
     <%= partial 'layouts/analytics_ga4_gtag' %>
+    <%= partial 'layouts/analytics_ga4_gtm' %>
 
     <meta content="IE=edge" http-equiv="X-UA-Compatible">
     <meta charset="utf-8">
