#GTMTips: Create Facebook Pixel Custom Tag Template

After the recent release of Custom Templates for Google Tag Manager, my mind has been occupied by very little else. However, I have a nagging feeling that due to how involved the feature set is, there’s still a lot of demystifying that needs to take place before templates are fully embraced by the GTM user base.

In this article, I want to show you a concrete example of template creation. It’s going to be much more ambitious than the simple walkthrough I explored in the main guide. This time, we’ll step through creating an actual, functional template that caters to a very specific use case: the Facebook Pixel.

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#GTMTips: Fetch the Latest Value of a Data Layer Variable

One of Google Tag Manager’s oldest and most reliable features is that it freezes the state of Data Layer variables to the moment when the trigger event occurred. Thus, any tags firing on this trigger (and any variables resolved on this trigger event) will always have access to the same value of each Data Layer variable.

However, there are situations where this is not a good thing. One is tag sequencing, and the other is a scenario where you want to run some custom code that should access the latest value of the Data Layer variable at a moment in time after the tag has already fired. Read on for an example!

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#GTMTips: Create Utility Variables by Returning Functions

In Google Tag Manager, the Custom JavaScript variable is an anonymous function with a return statement. It does not take any parameters, and by default it’s impossible to pass any parameters to it, because the Custom JS variable is simply resolved to whatever value the function returns. If it returns a number, for example, passing a parameter to it would make no sense and would result in a TypeError since the variable resolves to a number, not a function.

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#GTMTips: Use LocalStorage for Client ID Persistence in Google Analytics

Updated 1 October 2019 With ITP 2.3 it looks like Safari is reducing the usefulness of localStorage as well, so this solution should not be considered future-proof. The only stable way to persist client-side data at the moment seems to be HTTP cookies.

Updated 7 March 2019 - Added some extra caveats to this solution. Also, be sure to read my article on ITP 2.1, which has far more detail on what Intelligent Tracking Prevention is and how to work with it.

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#GTMTips: Use Enhanced Ecommerce Data Layer With Facebook Pixel

A recurring question in the Google Tag Manager communities (e.g. product forums) is how to use an Enhanced Ecommerce dataLayer object with the Facebook pixel code? It’s a common question since running a Facebook conversion pixel on a site that also collects data from the store into Google Analytics’ Enhanced Ecommerce reports is probably a very typical scenario.

Side note: Since Google+ is about to go the way of the dodo, I’ve created an archive of the entire community which you can browse and make text searches against.

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#GTMTips: Trigger Javascript Function Without Using a Custom HTML Tag

Last updated 9 October 2020: customTask updated to a more stable version.

The Custom HTML tag in Google Tag Manager is splendid. It’s your go-to tool when you need to run arbitrary JavaScript on the webpage. Some might even use it to actually add HTML elements to the page, but I’m willing to bet running JavaScript is its most common use.

However, there’s a downside to Custom HTML tags, which is only made more apparent on single-page apps which do not clear the full page when transitioning from one state to another. Custom HTML tags are injected to the end of <body>, which means you might end up with a lot of clutter in your Document Object Model.

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#GTMTips: Use Product-Scoped Custom Dimensions in GA Firebase

Thanks to the intrepid detective work of Jørn Reidel and Ahmed Marof, it looks like one of the big hurdles for doing a full migration from using the legacy Google Analytics and Google Tag Manager SDKs to the latest Tag Manager + Firebase SDK is now a non-issue.

The issue is, of course, Product-scoped Custom Dimensions or more specifically the lack of support thereof. Until now, I’d been holding against recommending the migration to anyone with Enhanced Ecommerce tracking set up simply because the documentation didn’t mention the possibility of sending these custom definitions to Google Analytics.

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#GTMTips: Use Click Variables With Element Visibility Trigger

If you are enjoying the Element Visibility trigger as much as I am, you’ll be glad to know of a very simple tip that might make your life easier when using Google Tag Manager.

The tip is this: If you’ve activated the built-in Click variables, they will be automatically populated with details about the element that caused the Element Visibility trigger to activate!

Tip 92: Use Built-in variables to analyze the visible element

Yes, it’s confusing they’re still named Click variables, especially since they’re duplicated in the Form variables, and even more so since they can be used with the Element Visibility trigger to identify which element became visibility.

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#GTMTips: Search DataLayer for a Key-Value Pair

One of the difficulties of working with Google Tag Manager and the dataLayer structure is that GTM doesn’t preserve history of the items collected into its data model. Or, at least, it doesn’t preserve it in a manner that would let us access it.

This is typically a very niche problem, but it does surface every now and then. For example, say you wanted to query whether an event with some specific value has already been pushed into dataLayer. Well, this is impossible, since any event you use to trigger this check would overwrite this previous event value in the data model (since any given key can only have one value at a time).

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#GTMTips: The Errors Tab in Preview Mode

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.

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