Overview of Built-in and User-Defined Variables in Google Tag Manager

Part 1: Built-in Variables

What are Built-in Variables?

Built-in Variables are pre-configured variables provided by Google Tag Manager. You must enable them before using them in Tags or Triggers.

Built-in Variable Groups:

Group	Common Variables	Description / Use Case
Page Variables	Page URL, Page Hostname, Page Path, Referrer	Track the current or previous page details
Click Variables	Click ID, Click Classes, Click Text, Click URL, Click Element	Capture what was clicked (buttons, links, etc.)
Form Variables	Form ID, Form Classes, Form Target, Form URL, Form Element	Trigger tags based on form submissions
Scroll Variables	Scroll Depth Threshold, Scroll Direction	Track how far users scroll down a page
Video Variables	Video Provider, Video Status, Video URL, Video Title, Video Percent, Video Duration, Video Current Time	Used when tracking YouTube video engagement
Error Variables	Error Message, Error URL, Error Line, Error Stack Trace	Capture JavaScript errors on your website
Visibility Variables	Percent Visible, Visible Element, Visible Classes, Visible ID	Trigger tags when specific elements become visible
History Variables	New History Fragment, Old History Fragment, New History State, Old History State, History Source	Used in Single Page Applications (SPA) to track URL changes
Utilities	Event, Container ID, Container Version, Debug Mode, Random Number, Timestamp, Environment Name	Helpful for debugging, environment tracking, or randomization

 How to Enable Built-in Variables:

1. Go to Variables in GTM.
2. Click “Configure” (top right).
3. Check the boxes for the variables you want to use.

Part 2: User-Defined Variables

What are User-Defined Variables?

User-Defined Variables are variables that you manually create in GTM to extract or transform data for use in tags, triggers, and conditions.

User-Defined Variable Types:

Type	Description	Example Use Case
Constant	Fixed value you can reuse across GTM	GA4 Measurement ID, Site Name
Data Layer Variable	Pulls data from dataLayer pushed by your website	Order value, user ID, product name
Auto-Event Variable	Retrieves properties of automatically tracked events (clicks, forms, etc.)	Capture clicked element’s ID or class
URL Variable	Extracts parts of the current page URL (hostname, path, query string)	Pull UTM parameters or page path
First Party Cookie	Reads a value stored in a browser cookie	Capture a session ID or language preference
JavaScript Variable	Accesses JavaScript values directly from the website’s global objects	Get window.location.pathname or other JS-based values
DOM Element	Gets content from an HTML element using CSS selectors	Capture <h1> title text or product name on the page
Lookup Table	Maps one value to another (simple value replacement)	Translate plan IDs to human-readable names
Regex Table	Similar to Lookup Table but uses regular expressions for complex matching	Map multiple URL structures to one standard value
Custom JavaScript	Lets you write your own JavaScript function that returns a value	Calculate values dynamically, combine logic, or return booleans

How to Create a User-Defined Variable:

1. Go to Variables in GTM.
2. Click “New” under User-Defined Variables.
3. Choose the variable type.
4. Configure it as needed.
5. Name your variable clearly and click Save.

Note: 

• Use Preview mode to see the actual value of variables when testing.
• Label your variables clearly (e.g., DLV – Order Value or JS – Pathname) for easier management.
• Combine Lookup Tables and Variables to organize complex tracking logic.