RockeCode

This plugin allows you to add Google Tag Manager scripts to your WordPress site. With this plugin, you can easily add your Google Tag Manager ID and the script will be automatically added to your site’s head and body tags.
<h3>Usage</h3>
Once the plugin is installed and activated, the Google Tag Manager scripts will be added to your site automatically. You can check in your website source code, in the head and body tags, to see if the script is being added correctly.
<h3>Disclaimer</h3>
By installing this plugin, you agree to use it at your own risk. The plugin is provided “as is” and we are not responsible for any damages caused by the use or incompatibility of the plugin. We make no guarantees that the plugin will work as intended and we are not liable for any loss or damage caused by the plugin.
This program is free software: you can redistribute it and/or modify 
it under the terms of the GNU General Public License as published by 
the Free Software Foundation, either version 3 of the License, or 
(at your option) any later version.
<ol>
<li>Tag Manager by RocketCode 1.1 settings</li>
</ol>

Tag Manager by RocketCode

Ronald Huereca

Marco Pereirinha

ruskinconsulting

Leon Hitchens

Integrate Google Tag Manager into your website.
The great thing about Google Tag Manager (GTM) is that you are able to gather most of your tracking scripts in one place. You can then fire these scripts whenever you want, specified by the rules you set up. This sounds great, right? Well it is. The only problem is that sometimes it takes a bit of implementing to set these rules up. This implementation can either be setting a dataLayer variable in the dataLayer before the tag manager script is loaded, or pushing a HTML event handler with the variable “event” to the dataLayer when a button is clicked. The problem is that this isn’t always that easy to do when you don’t have the ability/access to add the code to your site.
This is where the Metronet Tag Manager plugin shines. It really unlocks the power of the dataLayer so you can easily set macros and firing rules on almost any element.
This plugin lets you:
<ul>
<li>Easily add as many dataLayer variables on a per-post and per-page basis as you need.</li>
<li>The plugin already gives you six predefined dataLayer variables that you can change/remove or test the system with. These will be loaded on all pages and posts.</li>
<li>Set up separate dataLayer variables for pages that aren’t posts or pages (like archives etc).</li>
<li>Lets you easily add a HTML event handler to any content link with the GTM TinyMCE button in the WYSIWYG.</li>
<li>Lets you add your own unique ID or a class to each content link with the GTM TinyMCE button in the WYSIWYG.</li>
</ul>
Please note that for this plugin to work there is a slight customization that is needed. WordPress doesn’t let you load scripts straight after the opening tag which is where the GTM script needs to be placed to work correctly. To fix this you need to add <code><?php do_action( 'body_open' ); ?></code> just after the <code><body></code> tag and that’s it.
<blockquote>
Note, if you are using WordPress 5.2. and up, contact your theme developer and ask them to insert <code><?php wp_body_open(); ?></code> just after the opening body tag of their theme. Here is some code to <a href="https://gist.github.com/ronalfy/6b7f43e70e644320aba67d1876a0aeff" rel="nofollow ugc">show the theme developer to make it compatible with Metronet Tag Manager</a>.
</blockquote>
Please let us know if you have any feature requests or if you have any issues with this plugin.
Below are a couple of resources you might find valuable if you are new to Google Tag Manager
Official Google Tag Manager website 
https://developers.google.com/tag-manager/
Tracking Google Analytics Events with Google Tag Manager 
http://moz.com/ugc/tracking-google-analytics-events-with-google-tag-manager
Make Analytics Better with Tag Management and a Data Layer 
http://cutroni.com/blog/2012/05/14/make-analytics-better-with-tag-management-and-a-data-layer/
<h3>Filtering Variables</h3>
If you choose to place variable values inside percentage signs (e.g., %replace_test%), you can filter these as necessary.
Here’s an example:
<pre><code>add_filter( 'gtm_replace_test', 'gtm_replace_test', 10, 3 );
function gtm_replace_test( $total_match, $match, $post_id ) {
 return "replaced with content";
}
</code></pre>
The filter name is <code>gtm_</code> with the suffix of <code>replace_test</code>, since that content is inbetween the percentage signs.

Metronet Tag Manager

Simple, unobtrusive - great plugin. 

And whenver i see the name i always think
"If young metro don't trust you?"

This plugin is awesome

The plugin is helpful with installing Google Tag Manager. Works on WordPress multisite websites. The plugin is simple, straightforward, and more secure than a simple "insert headers or footers" plugin. 

Easily Add GTM to any Website

Integrate Google Tag Manager into  your website.

Tag Manager by RocketCode vs Metronet Tag Manager