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2. Tag management with a TMS

Tag management systems (TMS) are tools that make it easier to deploy and manage tags at scale. Typically, the management happens through a user interface, which controls how the TMS behaves on the web page to which it is deployed.

One of the biggest challenges with tags is how to manage them. As they always represent code that needs to be added to the site HTML or JavaScript, the risk of accumulating unnecessary technical debt is always present.

Tag management systems (TMS) can help with this. Instead of deploying each tag separately on the page, the site (ideally) loads only the TMS library. The TMS then takes control, deploying tags through its own mechanisms.

Tag management systems typically build their behavior on top of these three concepts:

  1. Tags, which represent individual image pixels, script loaders, JavaScript code snippets, or other resources that are executed in the context of the web page.
  2. Rules, which indicate when any given tag should be run.
  3. Variables, which can be used to provide dynamic content for tags.

In addition to these, most modern TMS rely on a Data Layer – a JavaScript structure on the web page designed to pass data between the web page and the TMS.

As a technical marketer, you will most likely work with a TMS at some point. Understanding the main benefits as well as the (often huge) risks that they introduce is important, if you want to efficiently tag a website for marketing purposes.

Tags, rules, and variables

Here is an example of a use case that could be formalized in a TMS.

Fire a tag when the user successfully subscribes to the newsletter, and send the user’s marketing preferences dynamically with the tag as custom parameters.

This use case nicely illustrates the core premise of a TMS.

Administrators can build tags, which always use the latest libraries and technologies made available by the vendors.

These tags can be set to fire (deploy / run) with rules that can be updated any time the underlying conditions change. For example, if the ID of the form in the use case above changes, it’s easy to change the rule logic in the TMS user interface.

Variables can be configured to not only pull values from the page or its structures, but also to normalize and sanitize the values before they are accessed by tags.


The variable that pulls in the marketing preferences in the example above can be configured to also rewrite any text in lower case letters to make sure that it is always in the same format when dispatched to the vendor. This is called normalization.

The impressive thing about a TMS is that all of these features are reusable. You can assign multiple rules to a single tag, and you can assign multiple variables to the tag and its rules.

For example, here are some examples of tags, rules and variables. All could be mixed and matched any combination you like.

Fire this tag……when this happens……using this dynamic data
Google Analytics 4 – EventThe page is first loadedPage URL
Google Ads – ConversionUser adds a product to the shopping cartUser ID
Facebook (Meta) – EventUser has stayed on the page for at least 10 secondsTotal dwell time on the page
TikTok – ConversionUser scrolls past the halfway mark of the pageScroll depth
Custom – Monitoring logUser logs inLogin method
Amplitude – EventUser navigates away from the pageFirst visit timestamp

The main benefit (and risk) of a tag management system is thus the speed at which data collection for marketing purposes can be deployed, managed, and removed.

Ease vs. accuracy

When first using a TMS, it’s easy to fall in love with it.

Before, it could take days or even months to get a small update to a marketing tag deployed by the site developers. Now, with a TMS, all it takes is a few clicks in the user interface and the tag will be running on the website.

This ease comes at a cost, though.

The faster something is to do in a TMS compared to without a TMS, the riskier it is.

While it might be tempting to scrape data directly from the page with some JavaScript variables in order to populate e-commerce tags with information, this can be very unreliable.

If anything changes on the page, these scraping variables can break, because the page state they reference would no longer exist.

Conversely, if e-commerce tracking would be set up properly with the help of developers, they could build a system which is more resilient to changes in the page.

While for many using a TMS is a way to escape the crutch of slow and unhelpful developers, paradoxically the most efficient way to use a TMS is in cooperation with web developers who manage the website.

Ready for a quick break?

Now’s a good time to take a small break – walk around for 5 minutes and have a glass of water. 😊

Tag management isn’t an isolated process

Because it is so easy to use a TMS, it’s tempting to isolate it completely from the web development process in your company.

This is not a good idea.

Even though the TMS is often managed by marketing teams, it is still a resource that runs on the website and has a direct impact on how the site experience is perceived by visitors.

A poorly managed TMS can become a performance bottleneck. It can leak user data to untraceable locations. It can break the site’s user experience. It can place the company into legal jeopardy.

The best operating model for a TMS is one where the marketing teams and site developers work together to build powerful data collection processes for marketing purposes.

Always, always make sure that someone in the company has full administrative access to the TMS. There is nothing as dangerous as a TMS that has been deployed on a web page, where sole access is with, for example, a marketing partner with whom the company no longer works.

The better the communication between all parties that have a stake in the TMS, the more resilient, robust, and reliable the processes activated through the TMS become.

Deep Dive

Things you CAN but probably SHOULD NOT do with a TMS

  1. Create new user interface elements on the page, such as pop-up banners or calls-to-action.
  2. Deploy heavy third-party libraries which negatively impact page performance.
  3. Use page scraping excessively.
  4. Overwrite site functionality, such as change what button clicks do.
  5. Collect more information about site visitors than they are voluntarily ready to share.

Key takeaway #1: TMS is a tag manager

Due to the versatile nature of a TMS, it’s important to remember its origin story: TMS is a tag manager. Its purpose is to consolidate and facilitate the creation and deployment of (marketing) tags. Avoid using it beyond this purpose. It’s not a light-weight CMS – it’s not supposed to change the page experience itself.

Key takeaway #2: Tags, rules, and variables are reusable

One of the best features of a TMS is how you can reuse rules and variables across tags. You can even reuse a single tag to serve dozens of different purposes with creative use of variables. This helps keep your tagging setup slim, but too much multipurpose utility can also backfire due to the resulting increase in documentation demand.

Key takeaway #3: TMS should not be an isolated process

The power of a TMS might make it tempting to completely isolate it from IT and developers. For example, you can use a TMS to scrape information directly from the web page without having to ask developers to update the data layer. This should be avoided. A TMS is the best fit in a collaborative environment. TMS use needs developer oversight to make sure that at the very least no data security or page performance issues arise from sloppy tag management.

Quiz: Tag Management With A TMS

Ready to test what you've learned? Dive into the quiz below!

1. Which of the following pose risks for any site that deploy a TMS? Select all that apply.

2. Which of the following is an example of a TMS "rule" in action?

3. Which of the following is not a key resource type of a TMS?

Your score is


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