February 8, 2021
Is Google Tag Manager Preview Mode Not Working? 18 Ways To Fix It.
IMPORTANT: October 16th, 2020. Google has just released a new version of the Preview and debug mode, which works completely differently. If you want to get familiar with it, watch this video first or read this blog post.
Updated: February 8th, 2021. Is Google Tag Manager Preview Mode not working? I’m pretty sure we’ve all been there at least once. This issue has caused some serious headaches in the very beginning when I started using it. Does this sound familiar to you? – GTM Preview and Debug mode is enabled but does not appear on your website (or appears, but does not function properly). Just don’t rage quit and read the following tips on how to fix Google Tag Manager Preview and Debug mode. I’m sure at least one of them will apply to your issue.
If you manage to solve the problem by yourself
If you find a solution to your problem by yourself (and that solution is not mentioned in this article), please let me know in the comments. I’ll make sure to update the guide accordingly, thus more people will benefit from it.
#1. GTM Snippet is Not Added to the Website
Here’s an example: you asked a developer to follow Tag Manager’s instructions and add container snippet to the website. After some time he completes the task but something’s not right here – Preview and Debug console still does not appear after you enable it. Turns out the snippet was never published to the live version of your website – a developer made a gawky mistake and somehow failed to publish changes.
There are two ways to verify whether the GTM snippet implementation:
- Use the Tag Assistant Chrome extension which checks for Google pixels on the page (e.g. Google Analytics, Google Ads, Google Tag Manager) and provides real-time feedback.
- Check the website’s source code. Click Ctrl + U (I guess it’s CMD + U for Mac users?) in your browser and look for GTM container code there.
#2. Wrong or Incorrect Container Snippet Added to the Website
Although this tip might sound silly, you should not ignore it. In order to verify, open your GTM account and check the upper right corner of the screen – see GTM container ID?. Compare it with the one which is added to your website’s source code.
Compare it with the one which is added to your website’s source code. Tag Assistant will help you do that.
Also, keep in mind that you or your developers should not modify the GTM container snippet. It must be added to the site exactly as you have copied it from the GTM interface.
#3. You Have Enabled GTM Preview and Debug Mode in the Wrong Container
The more Google Tag Manager accounts and containers you have, the bigger the chance you’ll eventually make this mistake. I have been there more than once and it keeps getting more and more frustrating every time. So do not forget to double-check whether the container is right. You can follow the method described in tip #2.
#4. You Need To Use The Same Browser
When Preview and Debug mode is enabled, it opens a new tab/window with the website that you are going to debug. If you then try to open Chrome’s incognito mode (or other browser’s private mode) that will not work.
#5. Recently created container? Publish it
If you have recently created a Google Tag Manager container and never published it, the Preview mode will not work. You can quickly identify if this applies to you by going to the Overview section of the GTM interface:
If you see Container Not Published text, do the following thing:
- Click the Submit button in the top right corner of the GTM interface
- If you already have a Preview mode’s tagassistant.google.com tab open, close it, and click the Preview button in the GTM interface once again. This step is important.
- Complete all the steps that the preview mode requires (e.g. enter the URL of the page)
#6. Try disabling preview mode’s query parameter
When you want to enable the Preview and Debug mode, it adds a gtm_debug=x parameter to the URL. This is default behavior. However, some websites do not support custom URL parameters, hence might not work (or throw things like “404 Page Not Found” errors).
If that is your case, try disabling this checkbox (see the screenshot below):
#7. Cloudflare Is Altering the Way GTM.JS Is Loaded
Note: I am not sure if this affects the new GTM preview mode but I kept this tip anyway.
This tip comes from our reader Chris.
A Content Delivery Network or CDN is designed to cache the static content on sites through a wide geographic network. The end result of using the CDN is that the static content will be delivered faster to the visitor from the network node in closest proximity to the visitor, thereby shortening the amount of time it takes the page load for your site’s visitors.
CDN also affects how JavaScript is pulled and gtm.js (Google Tag Manager’s JS library) isn’t an exception. If you’re using Cloudflare (a very popular CDN solution), make sure you have the feature called Rocket Loader disabled. I highly recommend consulting your developer about this issue.
#8. GTM code was accidentally modified while copy/pasting it to the developer
This situation happens when you want to send the GTM container code to a developer, copy it from tag manager’s interface, then paste it to some word file (maybe Google Docs or some other text editing tool) and then send the code to a developer.
Little did you know that the text editing tool “fixed” the container code according to certain grammar rules, maybe removed or added some spacing, changed apostrophes, etc.
Even though the code looks the same (at first sight), it won’t work (meaning that your Preview and Debug mode also won’t appear).
Here’s an example. On a website, a developer added GTM container snippet. However, if you take a closer look at apostrophes (in the screenshot below), they look wrong.
In JavaScript, apostrophes must be ‘ ‘, but in the screenshot below they are ‘ ’. Similar, but not the same.
A solution to this? Copy the GTM container code in the GTM interface and paste it to the .txt file (e.g. via Notepad), save the file and then send it to a developer. An alternative solution would be to copy the code and paste it to pastebin.com. Save the paste and then forward the link to a developer. When a dev opens the link, he/she will see the raw/unmodified code.
#9. Check if your browser is not blocking popups and redirects
When you click the Preview button in the GTM interface, a new tab or window will be opened that belongs to tagassistant.google.com. Sometimes, a browser might not like it and block it.
If you are using the Chrome browser, you might start seeing this in the GTM interface:
For me, this happens inconsistently. Sometimes, Chrome blocks the window, sometimes not.
Anyway, if you see that the browser blocked the tagassistant.google.com tab/window, click that icon and select Always allow popups and redirects… and click Done.
This enables this setting only for Google Tag Manager, so don’t be afraid of opening some pandora’s box.
If you are using a different browser, that “blocked” warning might look different. You will need to do some further investigation on your own.
#10. Try publishing the container (even if the container is not new)
Some people mentioned that they published the container before enabling the preview mode and it helped them. Since that moment, their debugging experience was smooth. I wasn’t able to verify it but it’s still worth a shot.
#11. Try exiting the preview mode and entering it once again
Close the preview mode’s tab, close the website tab. Then click the Preview button once again in the GTM interface and complete all the steps to enable it. This worked for me multiples times.
#12. AdBlocker, Ghostery, or Other Similar Extension Is Blocking GTM
Call it a feature or symptom of today’s web browsing behavior, but the ad and content blockers are making life for web analysts difficult.
Popular browser extensions like Ghostery, AdGuard AdBlocker, and AdBlock Plus make it easy to block Google Tag Manager, too. So if you’re using one of the blockers, try disabling them and see, whether it helped. So if you want to have a working preview mode, you’ll need to disable the extension.
Another plugin (that was reported by readers as interfering with the GTM preview mode) is Avira Save Shopping.
#13. Your website is using an automatic solution that blocks cookies from being set
With the dawn of GDPR and other privacy-related regulations, some website owners decided to use automatic cookie-blocking solutions connected to their cookie consent popups. Some examples are:
Unfortunately, I don’t have the specific steps on how to resolve this (because every tool will probably have different steps). But in general, you need to make sure that the cookie named _TAG_ASSISTANT (all uppercase) is allowed to be set.
It is necessary for the Preview mode to work. If you are not sure whether your website is using auto-blocking, consult with someone who is more familiar with your cookie-consent-management tool and the website that you are working with.
This will require some investigation from your side.
#14. Make sure you have selected to correct GTM container in the top left corner
If there are more containers on a site (but you have enabled the preview mode in just one of them), it’s possible that you are currently previewing the wrong container.
In the tool left corner of the Preview mode, you might see a little arrow-down icon. If yes, then click and check if you are previewing the correct container. If not, pick the right now.
Update: the design there looks a bit different now. The container IDs are more visible.
#15. You might be previewing a workspace instead of an environment
Note: try verifying your GTM environments even if you don’t see the same warning in your preview and debug mode (as I have described in this chapter).
Here’s a situation. You enable the preview mode and you see the message “No tags were evaluated in this container”. You don’t see any events (like Container Loaded) on the left side of the preview mode (all you see there is just the title of the page).
Also, you don’t see an arrow-down icon next to a GTM container ID at the top left corner of the preview mode. In that case, it’s most likely that you are trying to preview the workspace rather than the environment. It is quite confusing but let me try to explain. It will take a while to explain but this is important, otherwise, you might be even more confused.
When GTM is installed, usually developers add the GTM Container code that can be found by clicking on the container ID in the interface.
This is the regular GTM container snippet (not having any environment parameters). When you enable the preview mode by clicking the PREVIEW button in the top right corner of the GTM interface, you enable the preview mode for that particular snippet.
However, GTM offers the functionality of environments. You can create different environments, like development, staging, something else. In order to install it, your developer has to get separate snippets for each environment and place it in the respective versions of your website. For example, place the staging GTM container on staging.yourwebsite.com.
In order to get the snippets for environments, you need to go to Admin > Environments > Click Actions next to an environment > Get snippet, and then a developer should place it on the website. By default, there are two environments but you can create more if you need it.
Here’s the catch: if you want to create a custom environment like development or staging, create a new environment and get their snippets installed on respective versions of your website. But, when it comes to a live website, you should not use the LIVE environment’s snippet. Instead, click on the ID in the GTM interface and ask a developer to install that one.
So, where is the problem after all?
Sometimes developers add the Live environment’s snippet to the live website. That snippet looks a bit different compared to the default GTM snippet.
If you have an environment snippet (with additional parameters) implemented on the live site AND you try to enable the preview mode by clicking the PREVIEW button, it will not work. And you will get the “No tags were evaluated in this container” message. That is happening because you enabled the preview button of the current workspace (but not in a specific environment).
If you want to enable the preview move in the environment snippet, then you must go to Admin > Environments > Choose the environment that you want to preview (for example, it might be Live environment of your live website) > Actions > Share Link and then use that to access the environment.
Important: your GTM container must have at least one version published before you can see the Share Link option.
Yes, this might sound confusing and hopefully, the GTM team will improve the flow in the future. But if you are in fact dealing with GTM environments, the only way how you can preview the environment now is to go to Admin > Environments > Actions > Share Link.
And if you need this even on the live website, then ask developers to replace the Live environment’s snippet with the default GTM container snippet that you can find by clicking the container ID in the GTM interface.
How can you find out whether your GTM container (installed on your live website) is not using the Environment’s snippet? You will need to check the website’s source code (by using the View page source feature in the browser) and then compare that snippet to the default GTM snippet.
#16. Don’t use Brave browser while working with GTM
Brave browser is known to be blocking various endpoints related to Google. This includes Google Analytics, Google Ads, but also, Google Tag Manager. If Brave is your main browser, you have two options when it comes to working with GTM:
- Use a different browser just for work with GTM (e.g. Chrome or Edge because there are many useful GTM-related extensions)
- Or disable the main security feature of Brave browser called Shields
I would personally, just use a different browser because having Brave with Shields disabled makes it pretty much useless.
#17. Website’s domain is on http (not https)
I don’t know (yet) if there is any other workarounds for this, but it looks like GTM preview mode does not work if your site does not have an SSL certificate. In other words, the URL must contain https, not http.
If that is your case, it’s time to update and make your site more secure. Contact your developer/webmaster and ask him/her to add the SSL certificate and make sure that the web is loaded from https.
#18. Content security policy is blocking the GTM from loading
If your website has a Content Security Policy, it might block GTM’s preview mode. You can identify this by going to your browser’s developer console (On Windows, Chrome, you should go to Browser’s Menu > More Tools > Developer Tools > Console.
Then refresh the page. If you can find an error that looks like this (or something similar), this means that you are dealing with the Content Security Policy.
What does that mean? Your developers will have to update the CSP of the website. There are no workarounds, you won’t avoid developers here. Here are the instructions on what they should do.
Do you keep seeing the Preview mode badge at the bottom right corner of your screen?
I am talking about this badge:
If you continue to see it even after you have exited the GTM preview mode, read this blog post to resolve the issue.
None of the tips worked?
If none of these solutions helped you, please post a comment with the following information:
- A detailed explanation of what is not working. Some people report that they get a timeout, others say that they cannot see some events in the preview mode, etc. I need you to describe your situation in great detail
- Link to the website where this situation is happening
- Link to your preview mode. After you launch the preview mode, you are redirected to a tagassistant.google.com. When you enter your website’s URL and start previewing, copy the URL of that preview mode and share it in the comments. Don’t worry, if you publish the container at some point in the future, that shared preview mode will stop working.
GTM Preview Mode Not Working: Conclusion
Google Tag Manager’s preview mode allows you to browse a site on which your container code is implemented as if the current container draft was deployed.
Is Google Tag Manager preview mode not working for you? In this blog post, I outlined 18 tips on how you can make the preview and debug mode start working right away – from checking your cookie settings to using Tag Assistant.
If Google Tag Manager Preview mode is still not working for you (even after reading this blog post), post a comment below and we’ll come up with a solution.
If you have already found a solution that is not mentioned here, please share it in the comments with others.
I have also published a post on the most common Google Tag Manager mistakes (some of which were mentioned in this post as well). I might save you some time in the future 🙂
135 COMMENTS
yes yes, everything else is ok. I just started the preview mode again and same thing. Now only works when I refresh the page and then it pops up. Although normally it was open straight away when I opened the page.
But good that it works for most then haha :D
Hi,
Great list, would like to suggest one more. There was a new version of Chrome available and I just noticed it this morning. Updating and relaunching was the simple fix.
Thanks,
Jeremy
Turns out my problem was related to Cloudflare as this changed how the JS snippet was being pulled in. I changed to setting to optimise JavaScript and the preview mode started working.
Awesome tip! I'll include it in the blog post. Could you tell me where can I find this setting within CloudFlare (or what exact changes did you do)? Thanks!
I am using the W3ToalCache WordPress plugin and there is an integration with Cloudflare. The setting is within the W3ToalCache plugin in WP under extensions -> W3TC Settings -> Content Processing -> Then turn off "Rocket Loader". Having this setting on caused the GTM script to be surrounded in an alternative tag that affected the GTM preview mode. More information on this feature can be found here: https://support.cloudflare.com/hc/en-us/articles/200168056-What-does-Rocket-Loader-do-
Unfortunately I couldn't get rocket loader working in tandem with GTM by following their instructions as this should improve page performance. If anyone else can get it working I am sure it will help a lot of people.
Thanks! This is incredibly helpful. I'll update the blog post asap.
Try logging in to GTM account and trying to replicate the issue in Chrome's Incognito mode. Maybe some browser extension is interfering.
What do you mean by saying "I do not find any of my accounts after I login"?
Triple check if you are looking at the preview mode of the same container.
Cheers. Turns out the idiot dev had installed the GTM code on all pages but the home page. As soon as I visited an internal page, the debug console loaded.
I had no idea gtag.js and gtm.js are different things. I was thinking that since I had gtag.js installed, it was Google Tag Manager as well. And for a whole day I was troubleshooting why debugging preview mode wasn't working until I understood that I had to install GTM myself... Maybe that helps someone else as well.
Will preview mode work on a site that requires log in?
Yes
Wow. This worked! Thanks so much. I was having a lot of trouble, but this solved it!!! Thanks again.
I had a case where the problem was in the GTM code, which was not written in the HTML file but in another js file called in the HEAD, was solved by removing the GTM code from the JS file and pasting in HTML file
Hello!
In the new version, not a single one of my gtm.clicks are showing up in the preview/debug mode. Is is also happenning to anyone else? And how can it be solved?
Thank you!
Hi, do you have at least one All element clicks trigger enabled on a page?
Hello. Yes, I have all of them enabled actually. I just realized that none of them work on preview mode, then only work when published. Unfortunately, I’m not being able to test anything, just publishing :(
Same issue here
Can you share the link to your preview and debug mode and the website where this is happening? GTM team cannot replicate this issue hence it's difficult to fix it.
Same issue here. No tag fires in preview mode. The output in the preview window is "No tags were evaluated in this container". I have various pageviews, clicks, etc in my GTM container and none are visibly firing when testing using the preview mode. This appears to be a bug with GTM.
Hi, I have updated the guide with an additional tip that might help you solve the problem.
Same here. We have two containers: one for test website, one for live. the test container is working just fine, but the live container stopped working. Tried to setup the test container on live website to guarantee that it's not the website code. with test container everything works fine.
So it has to do with the live container. I have all click variables enabled and also several click and link click triggers.
custom events and pageviews are working fine.
Any ideas?
Hi Julius,
I got a new issue where it connected and then disconnected after a few seconds, not sure what is doing it...
Hi, does it happen on all GTM containers/websites or only on a certain one?
Can you try on another container/website? If the issue appears to happen only on a particular website, can you share the url of that website and the url of tagassistant.google.com?
Hi Julius,
I have tried 6 x other sites and they are fine, it seems to be just one. I have quite a few tags and triggers in the container. It is using latest GTM4WP plugin, and tried with and without debug url but still disconnects after a few seconds, i also have Adswerve turned off.
https://tagassistant.google.com/?cb=8055371684657917&waffles#!#source=TAG_MANAGER&id=GTM-WDT8L3T>m_auth=MEsI_nC-QTLmgVE0FWfT7Q>m_preview=env-6
Hi, try now. Also, I have updated this blog post with more tips.
#12 - If you are testing more than one page/URL, close all of the windows except Tag Manager and start over by clicking preview.
For me, I got the preview connected once, and then when I changed to check different pages/URLs, I kept getting a "Not connected" error on the website page and on the "Preview" page. Starting over resolved it.
thanks Gord - that worked for me - I had too many versions of the URL open. Once I shut them all down and then launched the debugger it connected and worked perfectly
I have another issue.
Don't know why, but now I have debugger popup with "No debugger found" on several pages - including this - and can't get rid of it (obviously, debugging is disabled and no domains listed in debugger).
Hi, read this to resolve the issue https://www.analyticsmania.com/post/4-ways-how-to-turn-off-google-tag-manager-debug-mode/
Every time I go to a subdomain the debugger drops the connection. The GTM pixel is installed and works across both properties, but when I click on a link that takes me to the subdomain it drops.
I did get the debugger to stay open once using Gord Marwicks' suggestion.
Hey, Rob, I wanted to ask for more details:
1. Did you close all windows and tabs (even non-GTM related)?
2. Or did you close just all the preview tabs and website debugging windows? (while keeping other non-related tabs/windows open.
Which option did work for you?
I had two Chrome Browser windows open to tab back and forth but removed all tag assistant related materials and left other Google items like GTM, Analytics, etc. open. And, other tabs open that were unrelated.
The one and only time it worked for me I only removed the Tag Assistant windows and the website I was debugging. Sadly, I could not repeat the success by trying that again and ran into the same roadblock.
Please feel free to reach me directly through email. Happy to screen share and troubleshoot together. Then hopefully present a solution for another item above.
In my case, I am dynamically loading the Gtm snippet, which was working fine with the previous preview mode in GTM. Now it shows "Tag Assistant could not connect to a tag on". I checked all the steps as mentioned by you, the only thing that works when i add gtm snippet manually in , but does not work when dynamically loaded.
I found a solution to it, but it's more of luck and doesn't know why exactly the previous thing not working. The project is built on react and in the index.js file i was calling the function that loads GTM scripts in head and body as provided by GTM. So, this time I tried using a library react-gtm-module that loads the GTM script and it works as expected.
Still figuring out why the previous case didn't work, will update as soon as find any answer about it.
Hi Julius,
First of all thanks for updating these and more articles regarding the new Preview & Debug version.
I was able to fix my time-out errors by applying solution #10.
But now I ran into the following problem;
The new Preview & Debug mode opens a new pop-up window, from which I can't change the fixed URL. Previously it was possible to navigate to a URL that cannot be reached through the website menu.
Is the above situation still possible with the new version?
Install Google Tag Assistant Chrome extension.
Hi Julius,
Thanks for responding so quickly.
I had already installed Google Tag Assistant, but it hadn't occurred to me to look into the extension yet, oops!
Just tried removing tag assistant plugin from browser, its now working for me
The page will open in new window but you can see the timeout issue will be no more
©2020 Google
Allthough I see the new debug mode has a lot potential, at this moment it is also very frustrating. When a website is on a development domain and behind a firewall (I can only get access if my IP-address is on the whitelist) GTM doesn't work. Like other posts I get the message "connected" and within a few seconds Tag Assistant says "Not connected". Which is so frustrating as it is on a development environment for a reason and I need to get to test the tags before the website is finished and goes to production...
Just before the release of the new version I could test without any problems. So it seems the new GTM needs some kind of access.
(At another website the staging environment is secured with a login and then there is no problem). Unfortunately the choice for the method of security is not mine to make...
Wow, this suddenly works. No changes on the side of hosting or development, none in my GTM settings, but it works. I get the idea Google debugged something themselves? Any clou? They don't publish any release notes?
There were many fixes published from their side.
Thanks for this article.
In my case it was the "Avira Save Shopping" PlugIn in chrome browser which came with my Avira Antivirus installation. After removing this plugin everything worked fine.
Hi Julius,
Nice info all step have checked but still, my debug mode is not working if my site doesn't have an SSL certificate is this issue or not.
thanks
Hi so this is crazy what Google did. Nothing works.
Right now I am able click PREVIEW in GTM, and then Tag Assistant window shows connceted to Container. The web page also says debugger is connected. However, when I look at the tag assistant window, it says:
"GTM-XXXXX is not enabled for debug"
To start debugging this container:
Go to Tag Manager
Open container GTM-XXXXX
Click the Preview button
Start new debug session
Which is exactly the thing I did so I am in this endless loop of broken!! Any ideas why?
If you see this, you need to select the correct GTM container in the top left corner of the debugger.
Hi, thanks for this detailed article, and for updating it for the new tool so quickly. Since this update we're no longer able to test though - it connects fine, but there are just no infos back in the debug window (variables, data layer, events etc) - nothing at all (except showing the different pages that have been navigated to, but not GTM info for that page). I've tried with and without the Chrome extension, but makes no difference.
Is this the link you're requesting in order to help out? https://tagassistant.google.com/#url=https%3A%2F%2Ffiit.tv%2F&source=TAG_MANAGER&id=GTM-KPFMTT7>m_auth=N31Puc189vSs87qTi4lu9g>m_preview=env-7
Thanks very much
That's a good tip. I thought people saw that dropdown. I'll update the guide soon.
I have a website which takes the customer information from x domain and populates the domin y with that information in the form. However if i give doain x url in the preview mode gtm gets disconnected as soon as it goes to domain y..the other thing i tried was using domain y url,, but in that case the form is empty since the information is lost when gtm reloads the page...any solution to the problem..
Every time I enter my domain for debugger mode, Google states it could not connect and the pop-up window shows a different website extension and previous a different website than mine. My website is https://www.xxxxx.com and it continuously changes it to https://www.xxxx.co.za and shows the wrong website in the preview. I have confirmed multiple times that I am entering it correctly and on the preliminary screens prior to the preview pop-up, the domain is correct. I have also tried to add a trailing slash and removing the debug signal in the URL. I am at a loss.
Hi, please share the URL to your preview mode and the URL of the domain that you enter in the preview mode.
https://tagassistant.google.com/?cb=5204809633310215#!#source=TAG_MANAGER&id=GTM-KNV4S3R>m_auth=QG-qnhTlMI9FlDygdzPMnQ>m_preview=env-8
https://www.redshedbrewing.com
Hi, as it was already mentioned in the guide, you must publish your container. Currently, it returns 404 error, which means that it is not published.
Hey guys, Im using a subdomain to qa and sometimes it shows connected but the windows in tag assistant never loads, this is the preview link: https://tagassistant.google.com/?waffles#source=TAG_MANAGER&id=GTM-5JRBXXZ>m_auth=gxXxHSZuE4p-lcyL-_sI6g>m_preview=env-3&url=https%3A%2F%2Fhomolog.sempreemcasa.dev
Hi, read the latest tip in the blog post (where I mention environments). I know that the symptoms of your issue look a bit different. But still, check that you are enabling the preview mode for the environment correctly (not via PREVIEW button but via Admin > Environments > Share Link)
This new tip certainly solved it in my case (mentioned above) - thank you!
The only thing that isn't clear is how you test changes *before* having to push them live to an environment - because what you describe previews a specific environment, which works well, but I'd like to test stuff before having to push it live (like we could with the old tool)
Tried to make it work but didnot, the link im sharing is already from the env I have for QA, can you see any other solutions?
https://tagassistant.google.com/?waffles#source=TAG_MANAGER&id=GTM-5JRBXXZ>m_auth=gxXxHSZuE4p-lcyL-_sI6g>m_preview=env-3&url=https%3A%2F%2Fhomolog.sempreemcasa.dev
I just tried your link and works just fine.
Hi Julius,
You are a hero for updating this article so fast after releasing the new debug design. I really like the update and I've worked with it for a couple days. However, since yesterday it suddenly stopped working.
I've tried all the above mentioned possible solutions, however, none of them works for me.
If I click preview in GTM I am redirected to tagassistant.google.com. There I type out the right website, and click "Start". The website opens and the bar goes halfway and stops there. Stays there for around 20 seconds and then says "Tag Assistant could not connect to a tag on http://eagledev.leadingcourses.com/en". However, in the tab with the new link opened I get the small screen in the right bottom saying that it is connected to the debugger with a specific emoji, and sometimes it says it could not find the debugger. However, in both cases the debugger on tagassistant.google.com is not working.
Some additional info: We are currently building a new website and I have Tag Manager installed on both the new and the old website. On the old website it works perfectly fine.
This is the URL to the debug session:
https://tagassistant.google.com/#url=http%3A%2F%2Feagledev.leadingcourses.com%2Fen
Hope you can help me!
Please provide the FULL url of the preview mode. This means that you must try to enable the preview mode (even if it fails) and copy that URL. It will contain many parameters.
This might be needed as well:
https://tagassistant.google.com/?waffles#source=TAG_MANAGER&id=GTM-55X4K6N>m_auth=Dhba_Ju9qjCJbRpulyHehA>m_preview=env-2&url=https%3A%2F%2Feagle.leadingcourses.com%2Fen
You are using the environment snippet. This is the error that I see (right-click on the image below and click "Open in new tab"):
Follow the latest tip added to the guide.
Hero! I asked a developer to change to the default GTM snippet. How did you get to these insights. Are you using an extension for this? If so, which extension? How can I replicate this?
No extension. Just need to look at the code.
My question is in addition to #15, our website has multiple environments like test, PreProd and production. Tip#15 is super helpful to debug the tags running on any of the environment. But I am still unable to preview my current changes in my workspace. In the previous version of GTM preview I was able to debug all the changes in workspace.
Unfortunately, you cannot view your current changes of the workspace in the environment. This is reported to Google, hopefully, they will fix it.
Ah ok, thanks for confirming - could you perhaps add that to the tip #15 then?
If we do want to do live testing, we should remove the "live environment" snippet, and use the "default snippet" which is the same thing anyway, right?
Hi Julius
The problem I'm having is that the GTM container sometimes loads and other times (at random) just doesn't. SO sometimes I see Message - DOM Ready - Window Loaded, but no container to fire the tags.
Any idea what could be happening here?
This is the preview URL: https://tagassistant.google.com/?cb=847854266750625#!#source=TAG_MANAGER&id=GTM-K3SLH5B>m_auth=HTCLZSisM80DdmjXCyEO2A>m_preview=env-6
Hi, What is the website URL?
Hi Julius, the URL is https:///www.amelior.be
You don't have Google Tag Manager on that website. That's why it's not working.
Hmmm weird. According to Google Tag Assistant and the 'Network' from the DevTools the container is added to the website... . I'll have to dig in deeper then. Thanks!
I just realized that I have to accept tracking to see the GTM container on a page.
So once I accept the tracking and then I try to enable the preview mode, it works just fine for me on your website.
I'm looking into solution #13. Where can I find the cookie named _TAG_ASSISTANT? I don't see it on several websites (including this one) if I check the cookies being set. How can I check if this cookie is being set or blocked?
You must go to the developer tools > Application > Cookies > your domain > and enter the cookie name in the search field.
If you don't find the cookie, it is not stored. I don't know how to check if something is blocking the cookie from being set. But if you have something like a cookie consent popup on a website and autoblocking feature enabled, most likely, that is causing the trouble.
Ah, I see. I must first activate the preview window. You're right, the cookie is not being set.
Autoblocking seems not to be enabled in this case (and Cookiebot is not yet configured so doesn't block anything yet, I would think).
But this does bring me a bit further. Something is blocking the cookie to be set. Now to find out what...
Thanks!
Hi Julius,
I tried almost all of those above from the hints given, but none seems to work. I'm trying to debug an AMP website, and Tag Assistant keeps telling me that "a timeout occurred". I don't use any ads blocker whatsoever btw.
Any thoughts?
Sadly did not help.
Issue is, if I go a a browser and access the site all activity appears in the Real Time reports.
If I launch the site in preview mode, my active doesn't appear.
I did change 1 tag and added 2 variables.
Need to test the changes before going live.
Have asked client if it is OK for me to publish before I confirm tags are working correctly. If they say yes I'll try that and see what happens.
Not happy with the new GTM preview functions.
Tried everything, still no luck, and some quite weird behaviours:
1. Website: https://mateuszdabrowski.pl
2. When I click the Preview in tag manager and provide my website details, it opens the page and in the bottom right I see the pop up informing me that the Debugger is Connected.
3. When I go to the Preview Debugger it is stopping at about 60% load and timing out. The tab name is "Tab Assistant [Connected]" but in its header on the top left there is red "Not connected".
4. When I then go to the main page of tag assistant I see that my domain is active and have a button to "Stop debugging". But when I click it, it opens my website yet again and the debugger does the same as in step 2.
5. I have two tags in GTM - GA3 and GA4 (as per https://www.analyticsmania.com/post/upgrade-to-google-analytics-4/) and the tag is already published, as I did not want to lose the data. GA3 is working perfectly fine, showing real-time data and the standard one. GA4 is showing nothing. Despite being in the same tag published at the same time (previously I was using GA directly, without GTM, so for both solutions, it is the first time in a tag for this page).
Tried multiple browsers (Safari, Chrome, Firefox) was blocking content blockers and cross-site cookie tracking, nothing helps.
I read 3 google support forums and 2 other articles before stumbling upon this one --- crazy stressed I couldn't figure out why it said my tag wasn't on my site when it definitely was.
It was #5!!!! So simple and yet no one said to make sure it got done.
THANK YOU!!! Downloading your GTM guide ASAP!
Hi Julious,
My site is created by using SINGLE PAGE APPLICATION. With this new version of the preview mode, Page views are NOT captured when I navigate between pages. Hence, I see all events grouped in one single page container.
The developer that is helping me suggested to use 'History Change' as an alternative for 'Page View' as trigger. Now I can see the tags firing when I visit specific pages, but they are still grouped under the same Page container. This is not ideal.
Do you have any other idea to make Preview Mode work in this kind of sites?
URL here: https://tagassistant.google.com/#url=https%3A%2F%2Fwww.flip.co.nz%2F%3Fgtm_debug%3Dx
This is how single page applications work. And the new preview mode has nothing to do with it. The previous version worked the same way. When you navigate between pages, the URL is dynamically changed and everything appears under the same "page" in the preview mode. Just switch between History events and see how tags are firing.
Thank you from Germany, didnt find such a complete article about GTM in german. Solved my problems. Thank you very much.
Here's a pesky one. Copied existing and functional page and pasted into a new file in Coda. Didn't realize I had the encoding incorrectly set. Page rendered fine, Google Tag Assistant sees it, no errors, but the debugger couldn't connect. Finally ran my page through https://validator.w3.org/ to figure out what the problem was.
Thanks! Had to go through all options to finally found out I had an extension called Disconnect which I forgot I had installed blocking it. Clicking "Unblock tracking" solved it. So if you're using this extension make sure it's allowing tracking on your website :)
Thanks for this article. Unfortunately, since this new version of GTM I can't succeed to make the preview work: "Tag Assistant could not connect to a tag on... A timeout occurred while attempting to connect." My GTM installation script is in the head, I tried with Google tag assistant or without any extensions activated in Chrome, I tried without and without "Include debug signal in the URL".. On Chrome, on Edge, on my different containers.. None work. I cannot find any solution to make this preview working.. An idea? Thanks
Hi Julius,
Thanks for these all guides. I love your articles.
My question is about GTM container.
I have a website and my website is copied by some people. All codes of my website is copied. So I can see visitor statistics of this copied version because my analytics code is also still in the code.
So I am thinking of using tag manager to intervene to copied version. I can create a HTML tag and add some style code that will make invisible all content like display:none.
I checked the GTM codes and yes, still my old GTM codes on the website. But GTM is not working. When I open the preview mode, debug mode works but find only gtag.js not GTM for this copied version.
Also GTM chrome extension find only gtag.js and analytics not GTM for copied version.
After my website is copied, the new page paths has index.html suffix. I dont know why there is index.html on the last of each page path. I guess this is related to copy system.
Can you help me? If I can make working GTM, I can intervene to copied version.
Possibly simplistic but it worked for me. Use Google Chrome as your browser, not Safari (for sure, possibly others). Hitting preview (in Safari) ran code but nothing happened, no window pop-ups etc. EVENTUALLY, I tried it in Chrome and it worked first time! Doh!
O`key guys! I found 1 way, spend on it solve 2 hours!
If you have Tag Assistant - do the connection to site, and when you see "Couldn't connect to.... and No debugger found" just RESTART (refresh) tag assistant on a page site.com/?gtm_debug=x, and you will see the effect! Good luck! i am from russia, sorry for my sentence and logic!)
Hi All,
I hope this comment will help some of you. It might be related to the comment made by Akim1337.
In short I couldn't preview my newly created and published container with a working tag (confirmed through GA dashboard) as I kept receiving "timeout" error in the Tag Assistant page and "no debugger found" in the previewed page. I believe I tried everything from the list in this post and please forgive me if my solution is there and I somehow missed it.
So solution first:
Remove Google Tag Assistant Extension from Chrome Extensions (disabling might help as well)
A bit more about the problem:
1. The new container features GA4 tags only
2. Container was implemented correctly and published with a basic Page View GA4 Event tag in it (I took a leap of faith not being able to test the first tag) - data flew to the property whcih I cinfirmed in Real Time report.
3. Any attempt to use Preview ended up with "0 container found" and "timeout" error in the tag assistant page and with "no debugger found" in the previewed page
4. Preview worked completely fine with other containers that contained GA3 tags
5. When Tag Assitant launched after hitting Preview button - the URL field just above the Start button was not populated with the URL of the page I was trying to test (which was the case for all the other containers)
All in all our IT suggested disabling all the extensions one by one and checking after each step if it has fixed the problem or not.
It worked after disabling Google Tag Assistant. If you have any suggestions for me to try and debug it further please let me know. Perhaps I missed some steps that would show it's a red herring - I am happy to help :)
Hi All,
Recently I had the most confusing experience, we were using zones to load containers in different apps and we also have a custom javascript variable to control what analytics property should receive the data, but because we had a zone restriction no tag was firing so if you are using zones make sure to check the zone restrictions because the assistant won't tell you if the tags did not fire because of zone restrictions
Another thing to try - this may just be coincidence - log out of admin on your Wordpress site. I kept getting "can't connect" errors whilst I was logged in as an admin. I logged out and it was ok connecting. May be coincidence.
Every time I visit to a new page on my website a new google tag manager installation appears on my Google Tag Assistant Chrome Extension.
I have not encountered this before. I am not sure what is going on. Has anyone else seen this?
Read this https://www.analyticsmania.com/post/multiple-installations-of-google-tag-manager-detected/
just came to drop you a huge thank you, your guide was SUPER HELPFUL
Great post! I ran into the timeout problem described by several people in the comments. For me, the culprit was the DuckDuckGo privacy extension in Chrome. I disabled it and things worked as expected.
Hello. In my case with the GTM preview mode ON, it shows events in this GTM window (precisely in the GA4 container next to UA container) but not in Analytics GA4 DebugView
Hi, sometimes debugview has some delays. Also, make. Sure you have selected the correct device in it.
Just spent a fair bit of time reading through a few of your troubleshooting guides but haven't solved my problem yet. I have a site (and due to some nondisclosure, I can't link you) where we have GTM installed (I've checked for punctuation problems, looks fine), GA tracking installed in the GTM container, plus some other tags. No environments, nothing fancy on the GTM side. I am getting the "Message" instead of "Container Loaded" thing you describe here: https://www.analyticsmania.com/post/pageview-trigger-not-working-in-google-tag-manager/ but the solutions there have not resolved this issue. I AM pretty sure at this point that the data layer is broken in some fashion, but can't be certain.
The really weird thing here is that while I can't get Preview to even show me a container load, Analytics is reporting plenty of visits (albeit significant losses, without recovery, after a new site design launched in 10/2020). Clearly the GTM container is loading for SOME users, but not in Preview. I am also pretty sure that my visits are not being recorded in Analytics, ie this container isn't loading tags for me, ever, in Preview or just browsing.
Right now I'm trying to get someone to look at the data layer, which is way outside my area of expertise (I'm an SEO and Analytics person, but I don't use GTM terribly often and I'm not a coder), whether there might be CDN issues involved, and review an age-gate popup to see if that's blocking cookies being set.
Do you have any other suggestions or things I should be looking at?
Update: there is no CDN involved, so that is not the issue. Developers are looking into data layer or cookie-based issues.
I was having issues getting the new preview to work in GTM. I still had the old Google Chrome Tag Assistant Chrome Extension installed the website would not connect in GTM until I clicked the Chrome extension to enable that. Then the site would connect with the new GTM preview.
Once I removed the GTM Tag Assistant Chrome extension the GTM preview connected to site right away. It seems that extension no being enabled on the page was causing the GTM preview to not connect.
Hi, I have a single page application. With GA4 the page views are firing on some of the pages and then suddenly stop tracking at the last 2 steps of the checkout. I am using a nuxtRoute event trigger of a history event trigger. Nothing works. Any ideas. I also dont see anything else load into the GTM tag assistant.
I've resolved the issue. In the GA4 admin interface on web streams details. There is an enhanced measures option. If you go into this and show advanced measures on page views you can untick Page changes based on browser history events, which stops another history event firing. This appears as event gtm.historyChange-v2
Same problem as many here.
GTM's preview mode isn't updating tags and triggers unless the container is published as mentioned in solution #10
Another issue I have, is that everything is delayed: the same values for click classes sometimes appear and sometimes don't. The same goes for firing tags and triggers which appear with the red X cross (when checking variables in the preview mode) and a bit later the green mark appears.
Worse, sometimes a tag that was working fine then stops firing when used a minute later then works (back and forth). Isn’t this going to mess up my analytics ?
This is very confusing as I can spend time trying to fix an issue that actually wasn't one. What is this?
Thank you for your help.
Hi, please share the link to your preview mode and describe what exactly does not work in it. I will take a quick look.
Thank you very much Julius.
Here are the share image buttons i'm tracking that are firing occasionnaly:
https://prnt.sc/xn4v79
here one of the tags fired: http://prnt.sc/xn59zg
Click Classes or preview mode are not "not working". It's just the way how those buttons are coded. Sometimes you click on a background of a button, sometimes on an icon. Thus you get different click classes. So the Preview mode works fine. You need to go more advanced with your click tracking or include additional conditions. Some additional tips https://www.analyticsmania.com/post/google-tag-manager-click-tracking/#css-selectors
Thank you very much !
I've resolved the issue. In the GA4 admin interface on web streams details. There is an enhanced measures option. If you go into this and show advanced measures on page views you can untick Page changes based on browser history events, which stops another history event firing. This appears as event gtm.historyChange-v2
Hi Julius,
Thanks for the blog!
I set up my GA through GTM for tracking. Also, GTM Code was inserted by the use of Magento. Now my Google Analytics records data when I apply a month range(That means GA is tracking data). The real issue here is, when I see real-time reports in GA and open my website in the next tab or on my cell phone I sometimes see myself getting counted as a real-time user, and sometimes GA doesn't count me as a user and shows zero number of the user. Now I am just skeptical about the reports I am looking at in analytics. There's no IP Filter applied in GA which is blocking it from tracking.
I have cross-checked my GTM and GA codes and they are configured correctly. Also, when I try to preview in GTM debugger it says not connected /time out error. I am just affraid is magento responsible for my GTM javascript code not loading properly in different browsers or something is blocking it from loading? (When I check my source code GTM head and body is present).
Thanks in advance. I will be glad if you could help.
Totally agree with the advice about Brave. I switched from Chrome to Brave a few weeks back because of the privacy issues. Quite happy with that. However yesterday I tried to test my various tags via GTM and Tag Assistant in Brave, and had huge issues. After trying Brave with shields down and various other work arounds, no joy. So, I went back to Chrome to do the GTM work, and all just fine. So, message is same as Julius's recommendation. Avoid Brave for any GTM work.
Great! My container wasn't published. Thank you.
Hi. Great post! Just wanted to share what I found.
After running through everything on this troubleshooting list, I finally figured out my connection issue was due to the Edge browser (Version 88.0.705.56 (Official build) (64-bit).
This morning, I woke up and thought to give Chrome a shot. Bingo!
For both Edge and Chrome and I have the same extensions running.
Hope this helps someone.
Thanks for this resource!
Actually, it was due to being logged into WordPress in the same browser. As soon as I logged out of the WP Dashboard, the debugger was able to connect.
Sites can block GTM or other unknown js scripts from running via content security policy (CSP).
if you've followed all the steps and still aren't able to see GTM/preview mode work, ask your devs/webmaster/IT team whether or not your site has a CSP implemented.
if so, the following values may need to be added to the CSP properties:
script-src: 'unsafe-inline' https://www.googletagmanager.com
img-src: www.googletagmanager.com
and to enable preview mode, some further CSP properties need the following domains added:
script-src: https://tagmanager.google.com
style-src: https://tagmanager.google.com https://fonts.googleapis.com
img-src: https://ssl.gstatic.com https://www.gstatic.com
font-src: https://fonts.gstatic.com data:
Thanks, I'll update the post.
I'll add another unexpected preview mode blocker...
If you're using Windscribe VPN's Chrome extension, it will somehow block the preview mode and cause a timeout error.
Thank You Mate! Really Appreciated.
Use two tabs to make it work. two separate windows of for example localhost:3000, while connecting to tag assistant.
Solution if none of the above worked!
Using Chrome Browser, check your Chrome Extensions. I removed any unnecessary extensions, including DuckDuckGo Privacy, EPUB Reader, McAfee and a few more and now it's connecting. So I'd suggest looking through chrome://extensions/ and seeing what you can remove to test it out.
Preview mode didn't work until I activated Tag Assistant Companion
Good luck!!
(sorry if it's repeated)
Thanks - worked for me!
My solution is to run VPN (for example in Opera). None solution in this article did not work for me. But VPN helped to connect to gtm.
Hello,
I'm a beginner in Google Analytics and Google Tag Manager, and I religiously followed the steps in your "How to Install Google Analytics 4 (with Google Tag Manager)" Youtube tutorial. But, when I click Preview, type the website URL, it shows "Not Connected" on top of the domain name on the upper left corner of the page, and below it, "0 Google containers found". On the pop-up, it says "Could not connect to the *domain name* and "Tag Assistant could not connect to a tag on *website url* - Retry button - "A timeout occurred while attempting to connect. Check that the page is tagged correctly and no errors have occurred." I tried the solutions listed here, except for #15 as I cannot comprehend how to do it, how to find the GTM code, and afraid that I might make a significant change to the website. Please help! Thank you so much.
Please share the link to your preview mode.
Hello Julius,
I'm so glad to hear back from you!
Here's the link once I click "Preview":
https://tagassistant.google.com/#/source=TAG_MANAGER&id=GTM-WD6P9QH>m_auth=3z0XWTC8CD6F4ZXO8DAHfQ>m_preview=env-4&cb=233945431905323
Here's the link after I type our website URL and begin the preview where the pop-up says it can't connect:
https://tagassistant.google.com/#/source=TAG_MANAGER&id=GTM-WD6P9QH>m_auth=3z0XWTC8CD6F4ZXO8DAHfQ>m_preview=env-4&cb=233945431905323
And finally, here's the link on the website that was launched from the preview function:
https://vancillary.com/?gtm_debug=x
Many thanks!
I hope it's okay that I've posted the links here. If it exposes us to anything or anyone that would mess up our website or get access without permission, would you be kind enough to delete my comment once you've checked on the links? I'd really appreciate it!
It's the first reason of my blog post. GTM container code is not added to your website. We are not talking here about the GA code. It's GTM code that's missing.
I hope it's okay that I've posted the links here. If it exposes us to anything or anyone that would mess up our website or get access without permission, would you be kind enough to delete my comment once you've checked on the links? I'd really appreciate it!
For me it worked by simply using Google Chrome instead of Firefox. Funny how I needed to google my issue before even thinking about that solution, but then again, why the hell shouldn't it work in Firefox *drunk smiley*.
Seriously need some help! I'm working on this website https://karlsgate.com/ and I've put in the GTM tag using headers and footers wordpress plugin. When I try to use preview mode it opens in a new tab (which is an improvement because last week it was opening in a new window). But the preview mode badge after trying to connect says "No debugger found." The tag assistant page says "Tag Assistant could not connect to a tag" and "A timeout occurred while attempting to connect." I have checked using the legacy tag assistant extension that the overall GTM tag is there (although I still don't see my tags & triggers firing).
https://tagassistant.google.com/#/source=TAG_MANAGER&id=GTM-5DB2LP4>m_auth=28vEPnx1MoQvdvXzEjs_Xg>m_preview=env-5&cb=4868435366233155
Just tried to use your preview mode's link and everything works fine. Try using the Tag assistant companion extension instead and uninstall the Legacy Tag Assistant. Also, try using the preview mode in Incognito mode in Chrome. If it works, the problem is in one of your Chrome extensions. You will have to figure out on your own, which extension is causing this. Disable them one by one.