4 Common Mistakes in Google Tag Manager That You Must Avoid

The purpose is simple, reduce the execution times or development of each site in order to devote as much time as possible to generate results; visits, customers and sales. Google Tag manager can help us get it as we've told you in this post, but only if the configuration is done well.

We are going to see some key errors that are usually detected in the GTM configurations and then suggest some helpful solutions, and of course, there are guidelines that are worth following as a whole. Get ready to take some notes, let's start!


The first mistake we could make in a Tag Manager is not to publish anything.

You arrive, you register in Tag Manager, you create the container, you edit your labels and you go to the page to check the changes but you do not get data from your site. Something fails.

If so, once you make a significant part of the changes in your GTM container, give it a try; check that in the preview everything works correctly and immediately afterwards press the Publish button. It seems very obvious but more than one @ we forgot to post sometime.

And of course, you'll ask "How often do I have to publish the Tag Manager container?"

Like everything, it depends on our needs. Sometimes with a simple change it is necessary to publish and others we can carry out many actions without doing so.

It is determined by what we are doing and the relevance of the modification, if it is high it is highly recommended to publish a new version and rename the one that we have just "uploaded" to production.


The Google Tag Manager Preview mode allows us to explore the site on which the container code is implemented as if the draft of the current container was implemented. After enabling Preview and Debug mode, a large orange notification sign will appear in the GTM user interface.

Once the preview mode is enabled, navigate to the site where the container is deployed and you will see a debug console window at the bottom of the browser which shows detailed information about the tags, including the activation status and which data they are processing.

Each time you make changes in GTM you must complete the following steps:

1) Click on 'Refresh' in the orange preview notification banner.

2) Update the browser tab of the site you are currently testing.


The trigger does not work. The tag does not jump, and to see why, we look in the Preview.

First it is important to go to the specific event where we expected it to jump to (in the left menu):

Then we scroll to where it says "Tags Not Fired On This Event", and we click on the label that we expected it to jump to: 


After that click, we go down to where the activation triggers are shown in detail and we will see this for example:

Well, one of the ways to solve this rather strange error ... is by unchecking the validation and waiting for the tags in this part of the activator (timeout setting or validation check): 


We must understand that we can NOT call a variable that has not been created / activated previously. Making reference to variables that do not exist is one of the most common mistakes when starting with GTM.

Unknown Variable Name

This happens when in a GTM configuration field we call a {{Variable}} does not exist. The variable is written well between double curly braces: {{Variable name}}, but this Tag Manager variable does not exist (it is not in our list of custom variables and it has not been activated or does not exist in the predefined ones of GTM). It is a very frequent error in GTM.

Another error in variables is usually the nomenclature. In the names of variables we have to refine with exact match of characters (Eye with accents, spaces, uppercase letters, etc ...)

There is no predefined nomenclature for the variables and certain other complex aspects (as a nomenclature of GA events), with which we define it and it is good to always follow the same system.

We are human, we all make mistakes and remember, it is always much cheaper to learn from other people's mistakes ;)

We hope this post will help you avoid at the very least the errors discussed above with the Google Tag Manager.

And how about you? Have you encountered any other errors in Google Tag Manager that you cannot solve? Get in touch with us and we will help you sort it out.



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Digital Marketing enthusiast - telling stories behind data

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