Off Site Services

Allows admins to add Google Tag Manager code to your site and use it only when site is switched to “Search Engine Visibility”.
Use Settings->Reading: check/uncheck “Search Engine Visibility” and add code to “GTM code fields”.

GTM Code Visibility

Easily add Google Tag Manager code to your site and use it only when site is switched to "Search Engine Visibility".

Joe Rhoney

AddFunc

Allows administrators to add code to the <code><head></code> and/or footer of an individual post (or page or other content) and/or site-wide. Ideal for scripts such as Google Analytics conversion tracking code and any other general or page-specific JavaScript. A very simple, reliable and lightweight plugin.

AddFunc Head & Footer Code

Easily add code to your head, footer and/or immediately after the opening body tag, site-wide and/or on any individual page/post.

GTM Code Visibility vs AddFunc Head & Footer Code