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Google Tag Manager (GTM)

How to Check if Google Tag Manager is Working

There’s no doubt that Google Tag Manager is a great tool. One of the benefits it brings is that, once implemented, it removes the need for (and burden on) developers to implement various technical requirements. In order to get to that point where everyone’s happy, you need to make sure that Tag Manager is even working in the first place.

With that in mind, here’s a couple of different ways to figure out if Google Tag Manager is working for you. They cover whether GTM has actually been installed properly and how to check if a tag is firing properly.

Check if Google Tag Manager is Being Loaded

To check if GTM has been implemented properly in the first place, we’re going to use the fantastic Tag Assistant (by Google) extension for Chrome.

Download the extension using the link above and you should see a small icon appear at the top right of your browser that looks like a blue shopping tag with a sideways smiley face on it.

Image result for tag assistant tag manager

This extension isn’t specific to Google Tag Manager, it looks at tags from a range of Google products such as Google Analytics, Google Optimize and more.

Now, once installed, load up the website that you’re using GTM on. Click the Tag Assistant icon in Chrome and click the Enable button towards the bottom left. This essentially ‘activates’ Tag Assistant so that it will start looking for and assessing tags as each page loads.

Once it’s enabled, refresh the page you’re on so that Tag Assistant checks it.

Clicking the Tag Assistant icon now will bring up a list of the tags that are present – implemented either correctly or incorrectly – on that page (see screenshot below).

The colours used for that tags are as follows:

  • Green – as you might expect, the tag has been implement correctly
  • Blue – the tag should be working fine, but there is at least one recommendation for improving its ‘health’
  • Yellow – ‘minor’ implementation issues have been found
  • Red – ‘critical’ implementation issues have been found

To get more detailed information about the status of a specific tag, just click on it.

In this case, the GTM tag is green meaning it’s been installed correctly.

If it’s yellow, the most common issue I come across is that the GTM container is empty. In other words, there are no tags in it (or no tags have been published yet). In this case, you can typically assume that it’s been installed correctly and once you publish a tag it will turn green.

If it’s red, click the tag to get a information regarding the specific error.

If the GTM tag does not show at all in that list, it means Tag Assistant can’t see the tag at all. Double-check that the code has been implemented, saved, uploaded and whatever else needs doing for the code to go live. You might also want to check that it’s been added to a file – such as the header – which is then included in every page of the site rather than just specific pages.

Check if Your Trigger is Firing

If Google Tag Manager has been implemented correctly according to the Tag Assistant extension, then the next thing we can check is that the triggers for your tags are actually firing. For this, we can use GTMs own Preview Mode.

Load up Tag Manager, go to the container you’re working from and click the Preview button at the top right of the screen. This will activate Preview Mode.

Load up the website that you’re testing and refresh it. This will bring up the Preview Mode ‘drawer’ that’s docked at the bottom of the screen. It helps you to debug issues by seeing exactly what GTM is doing.

Depending on how many tags you have installed and when those tags should fire, you might see your tags split into two sections; Tags Fired On This Page and Tags Not Fired On This Page. The difference is clear, but be aware that tags can fire on different triggers or events; if a tag hasn’t fired on the current page it doesn’t mean it won’t ever fire.

If all is well, when you carry out your desired action (which could just be loading the page) you should see your tag show up under the Tags Fires On This Page section.

If you expected your tag to fire and it didn’t, you need to figure out why the conditions were not met.

You can get more information about a specific tag by clicking on it. Scrolling down will show you details of the Firing Triggers – essentially the conditions for the tag to fire. Take a look at these and make sure they’re setup correctly.

By clicking on an ‘event’ in the list on the left of the Preview Mode window and then clicking the tag that you want to fire, you should see green ticks / check marks next to the conditions under the Firing Triggers section mentioned above. If you have multiple conditions, this can be a good way to see which are being met and which aren’t.

There are plenty of reasons why your tag might not be firing, but 99% of the time it’s because the conditions of the trigger are not being met.


By now I hope you at least have a better idea of whether or not Google Tag Manager is working properly.

GTM installation is relatively straightforward, especially when compared to figuring out why a tag isn’t firing when it should be!

If you’re still having trouble, let me know in the comments below.

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