While using the Google Tag Manager user interface around Halloween 2018, you might have noticed a new tab in Google Tag Manager’s Preview mode. The tab is named Errors and shows you the number of exceptions thrown by GTM’s tag templates on the page. In this short #GTMTips post, I’ll quickly walk you through what the tab shows.

Tip 90: The Errors Tab In Preview Mode

The tab’s name is an apt description of what the tab shows. If a tag template in GTM fails to fire due to an error, this tab would show details about the tag that failed and the error that caused it.

Note that it’s actually quite rare to have a tag throw exceptions if something goes awry. The Twitter tag, as in the screenshot above, is one of the rare tags that actually throws an error if you try to, for example, add an incorrectly formatted value as its parameter (plainvalue as the value of the content_ids parameter, for example).

If an error is thrown, you’ll see which tag threw the error and what the error was.

As you can see from the screenshot above, the error message isn’t always very helpful, but at least you’ll know which tag failed, and you can use this information to debug the tag thoroughly.

Time will tell if this tab will surface other types of issues with a container running on a web page!