Advanced concepts

Tag Managers

In previous chapter we have learnt what are events, pixels and tags. When you think about all possible events that needs to be tracked on modern website, especially eCommerce such as view product, add to cart, checkout, purchase and all event parameters - product details, categories, discounts, you may start to understand that it requires a lot of tags and those tags needs to be kept up to date with every small website change.

If tags are placed directly on a page, any change in a tag, introduction of a new ad platform, new event or even a new event parameter would require deploying changes to the website source code.

To avoid that, tag managers such as Google Tag Manager were introduced. They introduce an independent tagging workspace or container that can be managed by marketing team or tracking experts, they allow organising tags into folders or adding notes about each change.

As a result development team needs to place tag manager code on the website once, and from there all work can be done within tag manager.

Unfortunately, this is not enough. When you think about all possible data point that can be useful for analytical or advertising purposes you will realise that many of them are not easily available on the page. Things like all product categories, additional attributes, different ids like SKU, tax and shipping values, user-data aren't always easily accessible by tracking tags.

Even if they are visually present on the page, technically they are hard to use, their formatting may be wrong or the visual implementation can change often.

DataLayer

DataLayer is an invisible to end-user layer of data implemented as JavaScript array where website or integration developers can push all relevant data-point in a standard and convenient format.

For instance to track add to cart events, tracking expert could add tag via Google Tag Manager and try to scrape product details based on what's available in eCommerce UI. This is error prone and brittle option. If the add to cart action information with all relevant product details can be pushed to the website dataLayer then it becomes more robust and reliable solution.

That way all tags can trigger and read data in a standardised, reliable way, significantly improving tracking coverage.

UTM Tags

UTM tags although they are also called tags have nothing to do with website tagging. They are special parameters added to links that points to your website. In most cases it applies to links from paid campaigns.

They are conceptually a bit similar to dataLayer, they make tracking explicit. Without them attribution is based on multiple different data-points, like where the user came from, which may not be reliable. UTM tags, when added, make the source of traffic explicit and reliable.