Unknown Tag Type and Unknown Variable Type in Google Tag Manager

Here’s a situation: you enable the Google Tag Manager preview mode, but the tag is displayed as Unknown Tag Type for some reason. Or maybe you check the variable, and its type is displayed as Unknown Variable Type.

Why? This blog post will explain that.

It’s a bug

This issue started a while ago, but it has no real impact on how your tags work. It is just a bug in how tag or variable types are displayed in the preview mode. I don’t know what causes it. Maybe caching in Google Tag Manager, maybe something else.

I noticed that this happens only if you have just added a new variable or a new tag in the container. Once you enable preview mode, those new items can be displayed as Unknown Tag Type or Unknown Variable Type. However, if the preview mode gets refreshed several times and a little time passes, the tags will be displayed properly.

I don’t know how long you need to wait for the tag/variable to be properly displayed in the preview mode. But usually it is less than 1 hour. Sometimes, it might be longer. At worst, if you check the variable/tag the next day, it will be displayed fine.

I agree that this is inconvenient (because if the tag is displayed as “Unknown”, you cannot easily see what variable values were used with that tag).

However, as I have said, this does not affect the execution of the tag. The requests should still be sent (unless something is misconfigured in the tag).

Unknown Tag Type in GTM: Final Words

This happens randomly. Sometimes, newly added items are displayed properly in the preview mode, and sometimes, you get Unknown. I don’t know when Google will fix this. But in the meantime, don’t panic. Just be aware that this is a bug in how the tag is displayed (but it does not affect how the tag functions).

If you are implementing Google Analytics 4, then you should still verify the incoming data in the Debugview.