add_to_cart Event

The add_to_cart event is a core ecommerce tracking event. It captures a moment when a user adds a product to their shopping cart. This data is essential for understanding shopping behavior, funnel performance, and dynamic remarketing.

The add_to_cart model

The event model defines all properties needed to describe a user action of adding a product to the cart. This includes user and session identifiers, product-level metadata, pricing details, and optional hashed user data for privacy-safe matching.

Properties

Name
event
Type
string
Description
Must be set to add_to_cart.
Name
user_id
Type
string
Description
Unique identifier for the user performing the action.
Name
session_id
Type
string
Description
Unique identifier for the user's current session.
Name
ecommerce.currency
Type
string
Description
Currency code (ISO 4217), e.g., USD.
Name
ecommerce.value
Type
float
Description
Total value of the added items (after discount).
Name
ecommerce.tax
Type
float
Description
Tax value applied to the items.
Name
ecommerce.items
Type
array
Description
Array of item objects that were added to the cart.
Name
ecommerce.items[].item_id
Type
string
Description
SKU or product ID.
Name
ecommerce.items[].item_name
Type
string
Description
Product name.
Name
ecommerce.items[].item_brand
Type
string
Description
Brand or manufacturer name.
Name
ecommerce.items[].item_category
Type
string
Description
Main category the product belongs to.
Name
ecommerce.items[].item_variant
Type
string
Description
Specific variant info such as color, size, or edition.
Name
ecommerce.items[].price
Type
float
Description
Original item price.
Name
ecommerce.items[].discount
Type
float
Description
Discount applied to the item.
Name
ecommerce.items[].tax
Type
float
Description
Tax on this specific item.
Name
ecommerce.items[].quantity
Type
int
Description
Number of units added.
Name
user_data.external_id
Type
string
Description
Optional external user identifier for cross-system mapping.
Name
user_data.email_hash
Type
string
Description
Hashed email (SHA-256, lowercase, trimmed).
Name
user_data.phone_hash
Type
string
Description
Hashed phone (SHA-256, lowercase, trimmed).

Push event to the dataLayer

Here is an example of how to structure and push the add_to_cart event to the dataLayer:

dataLayer.push example

dataLayer.push({
  event: 'add_to_cart',
  user_id: '12345678-abcd-1234-efgh-1234567890ab',
  session_id: 'abcd1234-efgh-5678-ijkl-0987654321zx',
  ecommerce: {
    currency: 'USD',
    value: 49.99,
    tax: 4.00,
    items: [
      {
        item_id: 'SKU-00123',
        item_name: 'GlowMaster Smart Lamp',
        item_brand: 'LumaTech',
        item_category: 'Home & Living',
        item_variant: 'Matte Black',
        price: 59.99,
        discount: 10.00,
        tax: 4.00,
        quantity: 1
      }
    ]
  },
  user_data: {
    external_id: '12345678-abcd-1234-efgh-1234567890ab',
    email_hash: 'abc123examplehashedemail0987',
    phone_hash: 'def456examplehashedphone6543'
  }
});

Best Practices

Fire this event immediately upon item addition, not on confirmation.
Ensure hashes use SHA-256 and are pre-processed (trimmed + lowercase).
Always include currency and value fields.
Use GTM's Custom Event trigger to listen for add_to_cart events.

Use Cases

This add_to_cart implementation supports:

Funnel and drop-off tracking
Product-level conversion optimization
Dynamic remarketing campaigns
Cross-channel audience segmentation

Let us know if you'd like to add server-side examples, GTM setup steps, or Pixel integrations!