This guide explains the Container script implementation and Container noscript implementation options on the General tab and when to change them.
What these settings do
Google Tag Manager has two parts: a <script> block in the <head> and a <noscript> <iframe> right after <body> for users with JavaScript disabled. GTM Kit injects both for you. These two settings control how and where each part is loaded.
Container script implementation
| Mode | Behavior | Use when |
|---|---|---|
| Default | The container loads as normal, with async from the <head>. | Almost always. Recommended. |
| Idle | The container is loaded with requestIdleCallback, after the browser finishes laying out and rendering the page. | You are pushing for the highest possible Core Web Vitals scores and can accept that GTM-fired tags start a fraction of a second later, after first paint. |
The mode value 2 was used in earlier versions and is now treated the same as 1 (Idle). Existing installs are auto-migrated on upgrade.
The trade-off: idle loading improves perceived performance and Lighthouse scores, but a tag that needs to fire on initial page render (e.g. a heatmap that captures the first scroll) may miss its window. If you do not actively need idle, leave this on Default.
Container noscript implementation
The <noscript> fallback is what Google’s standard install instructions tell you to put right after the opening <body>. It exists so users with JavaScript disabled (and some bots and crawlers) still get an image-based pageview ping.
| Mode | Behavior | Use when |
|---|---|---|
| wp_body_open | The fallback fires on the wp_body_open action, which most modern themes call right after the opening <body> tag. This is the WordPress recommended location and matches Google’s official install instructions. | Almost always. Recommended. |
| body_footer | The fallback is moved to a body_footer hook (just before </body>). | Your theme does not call wp_body_open and you cannot change that. The <noscript> is technically valid here too, just less standard. |
If your theme is reasonably modern, mode 0 (wp_body_open) is correct. Themes built before WordPress 5.2 may not call wp_body_open. If yours does not, mode 1 is the workaround.
Steps
1. Open General settings
Go to GTM Kit, General.
2. Find Container script implementation
It is in the section that holds your container ID and container injection toggles.
3. Pick a mode and save
The default for new installs is Default. Change only if you have a specific reason.
Verify it worked
Open your public site, view source, and look for the GTM <script> block. In Default mode it will be a standard (function(w,d,s,l,i){...}) snippet inside the <head>. In Idle mode the surrounding wrapper uses requestIdleCallback.
For the noscript: look for a <noscript> containing googletagmanager.com/ns.html?id=GTM-XXXXX. In mode 0 it sits right after <body>. In mode 1 it sits at the end of the document just before </body>.
Common issues
Idle mode breaks first-page tags. Switch back to Default. Idle saves a few hundred milliseconds at most. If a tag misses initial load, that cost is not worth it.
The noscript does not appear in source. Either container injection is off (see Disable container injection), or your theme does not call wp_body_open and you are on mode 0. Switch to mode 1 (body_footer).