Google Tag Manager (GTM) blade

Usage in Liquid:

    ...
    {% include blades/gtm.liquid %}
  </head>
  <body>
    {% include blades/gtm.liquid for_body=true %}
    ...

Living example: /anydigital/blades/blob/main/_includes/blades/html.liquid

Usage in Nunjucks:

    ...
    {% include 'blades/gtm.njk' %}
  </head>
  <body>
    {% set for_body = true %}{% include 'blades/gtm.njk' %}
    ...

Living example: /anydigital/blades/blob/main/_includes/blades/html.njk

Parameters:

site.gtm_id - Your Google Tag Manager container ID (e.g., GTM-XXXXXXX)
site.prod - Boolean flag to enable GTM only in production
for_body - Boolean flag (default: false). When false, renders the script tag for the <head>. When true, renders the noscript fallback for the <body>.

How it works

{% if site.prod and site.gtm_id %}
  
    {% if not for_body %}

<!-- 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','{{ site.gtm_id }}');</script>
<!-- End Google Tag Manager -->

    {% else %}

<!-- Google Tag Manager (noscript) -->
<noscript><iframe src="https://www.googletagmanager.com/ns.html?id={{ site.gtm_id }}"
height="0" width="0" style="display:none;visibility:hidden"></iframe></noscript>
<!-- End Google Tag Manager (noscript) -->

    {% endif %}
  
{% endif %}