GTM Essentials

Core Google Tag Manager variables we set up on most accounts — first-party cookie readers, "does it exist" booleans, traffic source / ad placement, and a few page/post/form context values.

Keep the Starter Kit in sync. gtm-starter-kit/ bundles copies of every variable below so it imports self-contained. If you add, rename, or change anything here, update the Starter Kit export too — or the bundled copy will drift.

Quick import

gtm-essentials-variables.json is a GTM container export (documented here). Import it to create all of the variables below at once, filed under a GTM Essentials folder.

1. GTM → Admin → Import Container.
2. Choose gtm-essentials-variables.json, select your workspace.
3. Pick Merge and Rename conflicting so nothing existing is overwritten.
4. Preview, then Confirm.

Placeholder account/container IDs (0) are remapped into whatever container you import into.

What it creates (24 variables)

First-party cookies — 1PC - <cookie> (1st-Party Cookie variables):

Variable	Cookie	Platform
1PC - _fbc	_fbc	Meta
1PC - _fbp	_fbp	Meta
1PC - fbclid	fbclid	Meta
1PC - _gcl_aw	_gcl_aw	Google Ads
1PC - _uetmsclkid	_uetmsclkid	Microsoft Ads
1PC - _ttp	_ttp	TikTok
1PC - _twclid	_twclid	Twitter / X
1PC - li_fat_id	li_fat_id	LinkedIn

Cookie names are the common defaults for each platform — adjust the name parameter if a site stores a click ID under a different cookie.

Session variables (Custom JS) — each also lives on its own in this repo:

• cJS - Traffic Source — last-touch traffic source (cjs-traffic-source.js).
• cJS - Ad Placement — utm_placement, persisted per session (ad-placement.js).

Event deduplication:

• DLV - gtm.uniqueEventId — Data Layer Variable reading GTM's built-in gtm.uniqueEventId key (a page-local event counter). Exists to feed the variable below.
• cJS - Custom Event ID — globally unique event ID for Meta Pixel / CAPI deduplication, cached per {{DLV - gtm.uniqueEventId}} so every reference within the same event returns the same ID (cjs-custom-event-id.js).

Page / post / form context (Custom JS):

• cJS - Page Title — document.title (cjs-page-title.js).
• cJS - Post Title — the page's .entry-title / h1, falling back to og:title (cjs-post-title.js).
• cJS - Post ID — the WordPress post/page ID from the postid-… / page-id-… body class (cjs-post-id.js).
• cJS - Form ID — the id of the first <form> on the page (cjs-form-id.js). For the submitted form's id, use an Auto-Event Variable (Element ID) on a Form Submission trigger instead.

Built-in variables enabled — the import also switches on GTM's standard built-ins: Click Classes / Element / ID / Target / Text / URL, Event, Form Classes / Element / ID / Target / Text / URL, HTML ID, Page Hostname / Path / URL, and Referrer.

Analytics Client ID is intentionally left out — it has no stable container-export type, so enable it by hand in Configure if you need it (one checkbox).

All Variables Used

Custom Variable Name	Meta Parameter	GA4 Parameter	Value Type	Description
cJS - Ad Placement	ad_placement	—	String	Custom JavaScript variable that returns the ad placement for the session.
cJS - Custom Event ID	eventID (browser) / event_id (CAPI)	—	String	Custom JavaScript variable that returns a globally unique event ID so Meta deduplicates Pixel and Conversions API copies of the same event.
cJS - Traffic Source	traffic_source	—	String	Custom JavaScript variable that returns the traffic source for the session.
DLV - currency	currency	currency	String	The currency for the value specified.
DLV - gtm.uniqueEventId	— (internal)	— (internal)	Integer	GTM's built-in page-local event counter. Not sent anywhere — it's the cache key for cJS - Custom Event ID.
DLV - item_category	content_category	items[].item_category	String	Category of the page/product. Optional.
DLV - item_id	content_ids	items[].item_id	Array of integers or strings	Product IDs associated with the event, such as SKUs.
DLV - item_name	content_name	items[].item_name	String	Name of the page/product. Optional.
DLV - item_type	content_type	— (no GA4 equivalent)	String	Either product or product_group based on the IDs passed in content_ids or contents.
DLV - items	contents	items[] array	Array of objects	Array of JSON objects with product IDs and quantities. id and quantity required.
DLV - num_items	num_items	— (sum of items[].quantity)	Integer	Used with InitiateCheckout. Number of items when checkout was initiated.
DLV - predicted_ltv	predicted_ltv	— (GA4 computes pLTV internally)	Integer, float	Predicted lifetime value of a subscriber as defined by the advertiser.
DLV - search_string	search_string	search_term	String	Used with the Search event. The string entered by the user.
DLV - status	status	—	Boolean	Used with CompleteRegistration to show registration status. Optional.
DLV - value	value	value	Integer or float	The value of a user performing this event to the business.
—	delivery_category	shipping_tier	String	Type of delivery for a purchased product: in_store, curbside, or home_delivery.
—	— (no Meta equivalent)	transaction_id	String	Unique ID for the transaction. Required for GA4 purchase and refund events.