Here’s a list of built-in variables available in Tag Manager.

Variable name	Variable ID	Description
CDP Audience*	46505189-34d1-4d98-8418-bd827c3a7c57	The variable stores a list of audiences the visitor belongs to. It’s only available when Data Activation (formerly CDP) is enabled for the organization.
Campaign	a3f51ab7-ea76-4adc-a839-a32d392df37c	Its value is based on the utm_campaign or pk_campaign parameter from the URL.
Click Classes	efc09356-e1f2-40f7-8a0a-4c454429e678	Contains a class or multiple classes of the clicked element. The value updates when a visitor clicks an element with the selected CSS class.
Click Element	db5a673e-dabe-4dfa-908c-d08b369d08c9	Contains DOM object of clicked HTML element.
Click ID	f39468e9-ae2d-4e58-9e2c-73a4d44add6f	Contains the ID of the clicked element. It changes its value when the visitor clicks an element with the chosen ID.
Click Url	efd3558a-714d-4b33-9edd-2bbeb0b5eaf7	Contains the URL of the clicked element. It changes its value when the visitor clicks a link with the chosen URL.
Consents	67f49c79-bab6-4b0f-95c8-3bf624b6398f	Contains information about the current and previous state of visitor consents.
Event	977a1f9d-4fdb-43bf-9549-bdf68a7b69a6	The name of the event emitted on dataLayer. It changes its value when a chosen custom event occurs in dataLayer.
External referrer	6fa9617f-00b8-4bed-8112-ccbb32033c74	The URL of a page from another website, with a different hostname, that linked to your current website.
Form Classes	d7c47336-342d-4c9b-b35a-fa13f238ca44	Contains the class(es) of the submitted form element. It changes its value when the visitor submits a form with the chosen CSS class.
Form ID	b1504526-de0d-4c27-9ff0-1ee7734561ed	Contains the ID of the submitted form element. It changes its value when the visitor submits a form with the chosen ID.
Form Name	028f3993-dc39-4ad1-8602-f6345c91f3bb	Contains the name of the submitted form.
Form Url	0e45761b-d00d-4b18-88c1-eb8fc233d3da	Contains the URL of the submitted form element. It changes its value when the visitor submits a form that sends a request to the chosen URL.
Found Elements	7dead2a9-5804-4cdd-8d73-b04d338952e9	A variable used in the element presence trigger. It contains the class name of the elements the trigger is set to detect.
History fragment	d462fb15-d23c-40e2-bc54-494377accccb	Contains the current value of URL fragment identifier (hash). It changes its value when a hash in the page URL meets a defined condition.
History source	caf01b44-cdbf-4a7e-a7e8-0150744b4e32	Contains information about the last method/event that updated the history object. It changes its value when a pushState, replaceState, popState or hashchange event occurs.
History state	c98aff1e-a24a-4ab7-bad4-d7e0f056b42e	Contains the current value of HTML5 history state which is of type any. It changes its value when a history state meets a defined condition.
Leave content	c2fe42d6-2cbc-45d0-b4df-af92fdbdc2fc	It changes its value when the cursor leaves a page. You can choose two options for this condition: page exit intent — the cursor leaves page via top edge or cursor leaving the browser's area — the cursor leaves page via any edge.
Old history fragment	44ef5a4b-4009-4f66-8fb4-c8137c0ed1b0	Contains the previous value of the URL fragment identifier (hash). It changes its value when the previous hash in the page URL meets a defined condition.
Old history state	a489adb8-f2cf-4a09-8b7a-e6a048b943d7	Contains the previous value of the HTML5 history state, which can be any type. It changes its value when the previous history state meets a defined condition.
Page Hostname	42ff090e-f97c-45b5-8625-21ae26891382	Contains the hostname from the URL of the current page.
Page Path	e1e2b185-464f-4eb5-8575-feec34c5e281	Contains the URL path of the current page.
Page Scroll	a9a87b7d-d565-433d-8090-df9d80bf91f5	It changes its value when the visitor scrolls to the chosen point on the page. For example, the visitor scrolls 50% of the page or scrolls to 1440 px on the page.
Page Url	67ed6060-eace-4370-8ede-a083f7c909f1	Contains the full URL of the current page.
Referrer	8530b589-aaac-42e4-b4c0-dfeef1360ee5	The URL of the page that linked to the current page.
Returning Visitor	d76335ca-0ae1-4540-8b7e-5ff7acb0d14f	A logical condition that determines whether this is the user's first visit. Its value changes when a returning visitor clicks an element on the selected page. This mechanism is based on cookies.
Time on website	4a3cbab8-e239-44ca-b1c9-6c1bc5cc3fbd	Its value changes when a visitor stays on the website or page for a specific amount of time. For example, it triggers a tag when a visitor spends at least 15 seconds on a page or website.
Traffic source	78fec807-3991-4fbc-ad57-238a6960d0b7	Contains traffic source: campaign, organic search, social, website, direct. It changes its value when the visitor clicks an element on any page to which they came from the chosen traffic source: campaign, organic search, social, referral, direct.
View within session	18c827bd-43e2-409a-a25d-cd8b0f6b95f7	Contains time in seconds from last interaction.

* The module is now called Data Activation instead of Customer Data Platform. However, the variable name will stay the same for now to ensure compatibility with older code.