October 21, 2020
Multiple installations of Google Tag Manager detected by Tag Assistant: What to do?
Updated: October 21st, 2020
“Multiple installations of Google Tag Manager” – says Tag Assistant. This is a fairly common “issue” noticed in online communities. The reason why I surrounded the word issue with quotation marks is that usually, this warning is no issue at all.
Here’s what I’m talking about:
What looks really concerning in the screenshot above is the fact that the same container is added multiple times to the same page. At least Google Tag Assistant says so. But you’re probably pretty sure that the GTM container is added only once. So what the heck?
What is going on?
Update: the recent update of the Google Tag Manager Preview mode on October 16th, 2020 is not causing this as well. I have added an additional chapter at the end of this blog post
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So if you’re seeing a message that Multiple installations of Google Tag Manager are detected and their IDs are actually the same, I have a hunch that you’re working on a Single Page Application.
If yes, then most likely, there is nothing to worry about (but just to double-check, continue reading).
Unfortunately, Google Tag Assistant is quite buggy when it comes to debugging Single Page Applications. Even though only one GTM container is installed, Tag Assistant may display multiple container instances as the app loads or a visitor continues to browse. This does not happen on ALL single-page applications but is quite often nonetheless.
What should you do?
To verify whether you actually have multiple installations of Google Tag Manager, check network requests in browser’s developer tools. In this demo (and as always), I’ll be using Google Chrome.
In the top right corner, click 3 dots, then go to More tools > Developer Tools.
Switch to Network tab and in the search field enter “gtm.js” (without quotation marks), keep All selected, and refresh the page.
After the page has reloaded, take a look at how many gtm.js do you see?
If one, you’re good to go. Just ignore Tag Assistant’s warning about multiple installations.
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IMPORTANT: You should do this verification when you have disabled Google Tag Manager’s preview mode. If you see multiple gtm.js requests only when the preview mode is enabled, jump to the next chapter of this blog post.
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If on the other hand, you see multiple gtm.js (while having the preview mode disabled), this means that there certainly are multiple GTM container snippets loaded on a page. Is that expected? Was it intended to have multiple containers on the same page?
Have a discussion about that with someone who might know the project/website you’re currently working on. Even though it isn’t optimal to use multiple GTM containers, it is possible. You can learn more about this here.
If nobody intended to have multiple containers on the same site, just remove one that shouldn’t be there (or ask someone to do that).
Multiple requests because of GTM Preview Mode
If you have enabled Google Tag Manager’s preview mode, you will be seeing two gtm.js requests in the network tab or in Tag Assistant Chrome Extension. Also, if you have some gtag() codes on your site (or Google Analytics 4), you will see their duplicate requests as well.
But don’t worry, this is expected. If you see two gtm.js requests for the same container (you can see that by looking at GTM-……) but the 2nd request contains gtm_debug=x, it’s fine.
The 2nd request is needed for the preview mode to work and it does not affect your tags or data quality. The same applies to Google Analytics requests coming from gtag(). If you see more than expected requests and some of them have the gtm_debug=x parameter, this is needed just for the preview mode.
If you exited the preview mode and refreshed the page, you’d see that 2nd request is gone.
Hopefully, one day Google will update the Tag Assistant Chrome extension to ignore the 2nd request. But I am not sure if/when this would happen.
Multiple installations of Google Tag Manager – Final words
To sum up, if you see this error in the Google Tag Assistant Chrome extension and you’re working on a single page application, most likely this error is just a Tag Assistant’s bug. For some reason, the extension doesn’t play very well with SPAs.
Also, you might see that error if you have enabled GTM’s preview and debug mode.
To make sure that the website is indeed using just a single GTM container, check requests in the browser’s developer tools.
15 COMMENTS
Cool little debugging example, Julius - thanks!
In fact just yesterday I saw an example of multiple GTMs (on glassdoor), but they actually do have multiple GTM containers running - as evidenced by different container IDs in Google Assistant AND through your network example.
I learn something every day from you!
Very nice blog, thanks! Luckily I haven't had this issue yet.
I too was confused at the beginning when I saw that message in the console. I just figured out in my case the Optimize installation (which also has a GTM id) causes this error. So maybe that's a possible explaination for others too.
Yes, forgot to mention. This also can apply to other Google Tags as well, e.g. Google Ads Remarketing Tag or Optimize (but their requests in the Network tab are different compared to GA).
Really enjoy the content you are producing! I recently took your GTM advanced course.... love it!
Thanks. I've been looking all over, trying to figure out where all the installations are.
Turns our, after following your post - there's only 1.
Great post.
It was a very confusing issue.
If multiple Google Ads Remarketing Tags are implemented on same page with different ID will that trigger multiple GTM on that page?
Hi, no. Those are two different things.
I am Adobe Launch user. I have two different rules to trigger gTag global and Google Ads tag. But dataLayer is defined in gTag global rule. Google Ads event snippet is also pushed to the same dataLayer. I see 2 gTag global loading on the page one with gTag global rule and one with Google Ads rule. I need to reduce the gTag global getting triggered multiple times. How can I do that?
Those tags are not google tag manager tags (ignore the googletagmanager domain in those tags).
Both tags you have serve different goals, keep them as they are. At least that is what I would do.
Thanks! It really helped! I guessed that Tag Assistant was buggy, but now I'm sure of it :)
thanks for the input, but I'm still confused, can I or can't have 2 differents GTM on my website. Let say we have 2 differetn marketing company doing marketing to us and we don't want both see each other data can each one have their own GTM and I added both on my website does this affect anything on bad way ? thanks
You can. But that will cause problems and conflicts between the two containers. It is not recommended.
Helped a lot! Followed your little guide and found out there was only one tag installed despite Tag Manager saying there were multiple.
Thank you :-)