add_to_cart

The add_to_cart event is your most actionable funnel event. It’s the moment of commercial intent — the user has moved from browsing to buying. The conversion rate from view_item to add_to_cart is one of the most important product performance metrics you have.

Get the details right: value must reflect the actual quantity added (price × quantity), not just unit price. The item_id should be the variant-level SKU when variants exist. And the event should fire on successful cart addition, not on button click — if your cart is API-based, fire after a successful API response.

When to fire

Fire add_to_cart when:

• User clicks “Add to Cart” on a product detail page (after success confirmation)
• User uses a quick-add button on a category page or recommendation widget
• User increases quantity in the cart (for the delta added, not the total)
• User moves a wishlist item to the cart

Fire after confirmation, not on button click. If your add-to-cart is an API call, fire after the successful response — not before, in case the call fails.

Complete dataLayer push

// Always clear previous ecommerce data first
dataLayer.push({ ecommerce: null });

dataLayer.push({
  event: 'add_to_cart',
  ecommerce: {
    currency: 'USD',
    value: 179.98,   // price × quantity: 89.99 × 2
    items: [
      {
        item_id: 'SKU-001-BLK-L',
        item_name: 'Classic Leather Jacket',
        item_brand: 'Heritage Co.',
        item_category: 'Apparel',
        item_category2: 'Outerwear',
        item_category3: 'Jackets',
        item_category4: 'Leather',
        item_variant: 'Black / Large',
        price: 89.99,
        quantity: 2,          // user added 2 units
        index: 0,
        affiliation: 'Online Store',
        coupon: '',
        discount: 0
      }
    ]
  }
});

Notice value: 179.98 — this is 89.99 × 2, reflecting the total value being added to the cart. value on this event represents the monetary value of the add action, not just the unit price.

Event schema

Event Schema add_to_cart

Parameter	Type	Required	Description
event	string	Required	Must be "add_to_cart"
ecommerce.currency	string	Required	ISO 4217 currency code.
ecommerce.value	number	Required	Total value being added — price × quantity for each item. Must be a number.
ecommerce.items[]	Array<Item>	Required	Array of items being added to cart. Usually one item, but can be multiple for bundle add.
items[].item_id	string	Required	SKU or variant-level product identifier.
items[].item_name	string	Required	Product name.
items[].item_brand	string	Optional	Brand or manufacturer.
items[].item_category	string	Optional	Primary product category.
items[].item_variant	string	Optional	Selected variant — color, size, style.
items[].price	number	Optional	Unit price at time of add. Not the line total.
items[].quantity	number	Optional	Number of units being added in this action.
items[].affiliation	string	Optional	Store or seller affiliation.
items[].coupon	string	Optional	Item-level coupon code if active.
items[].discount	number	Optional	Monetary discount applied.

Handling different add-to-cart patterns

Quick-add from a product list

When a user adds a product directly from a category page or search results without visiting the PDP, include the list context from the list they were viewing.

// Quick-add from category page
dataLayer.push({ ecommerce: null });
dataLayer.push({
  event: 'add_to_cart',
  ecommerce: {
    currency: 'USD',
    value: 24.99,
    items: [{
      item_id: 'SKU-047-WHT-M',
      item_name: 'Cotton Crew T-Shirt',
      item_brand: 'Heritage Co.',
      item_category: 'Apparel',
      item_variant: 'White / Medium',
      price: 24.99,
      quantity: 1,
      item_list_id: 'mens_tops',       // list context preserved
      item_list_name: "Men's Tops"
    }]
  }
});

Adding multiple items at once (bundles)

For bundle products or “complete the look” features that add multiple items simultaneously:

dataLayer.push({ ecommerce: null });
dataLayer.push({
  event: 'add_to_cart',
  ecommerce: {
    currency: 'USD',
    value: 154.48,   // sum of all items: 89.99 + 24.99 + 34.50 + 5.00
    items: [
      {
        item_id: 'SKU-001-BLK',
        item_name: 'Classic Leather Jacket',
        price: 89.99,
        quantity: 1
      },
      {
        item_id: 'SKU-047-WHT-M',
        item_name: 'Cotton Crew T-Shirt',
        price: 24.99,
        quantity: 1
      },
      {
        item_id: 'SKU-112-TAN',
        item_name: 'Woven Leather Belt',
        price: 34.50,
        quantity: 1
      },
      {
        item_id: 'SKU-088-BLK',
        item_name: 'Leather Card Wallet',
        price: 5.00,
        quantity: 1
      }
    ]
  }
});

Incrementing quantity in cart

If a user changes quantity in the cart from 1 to 3, fire add_to_cart for the delta (2 units added), not the new total. If a user decreases quantity, fire remove_from_cart for the delta removed.

// User changes quantity from 1 → 3 (added 2 more)
dataLayer.push({ ecommerce: null });
dataLayer.push({
  event: 'add_to_cart',
  ecommerce: {
    currency: 'USD',
    value: 49.98,    // 24.99 × 2 (the 2 units being added)
    items: [{
      item_id: 'SKU-047-WHT-M',
      item_name: 'Cotton Crew T-Shirt',
      price: 24.99,
      quantity: 2    // the delta — not the new total of 3
    }]
  }
});

GTM configuration

1. Create a Custom Event trigger. Event name: add_to_cart. Name it CE - add_to_cart.

2. Create Data Layer Variables for ecommerce.currency, ecommerce.value, and ecommerce.items.

3. Create the GA4 Event tag. Event name: add_to_cart. Enable Send Ecommerce data. Add currency and value as explicit event parameters.

4. Test in Preview mode. Add a product to cart. Check that quantity reflects how many were added, price is the unit price, and value is the product of the two.

Common mistakes

value equals price regardless of quantity. If the user adds 3 items at $24.99 each, value must be 74.97, not 24.99. GA4 uses value to measure the monetary impact of each add event.

Firing on button click before API confirmation. If the API call fails (item out of stock, session expired), you’ve tracked a cart add that didn’t happen. Fire after the success response.

Using the parent product ID instead of the variant SKU. If the user selects “Blue / Large,” the item_id should be the variant-level SKU. Using the parent ID means you can’t analyze which variants are most popular by add-to-cart behavior.

Treating cart quantity update as a new add_to_cart. If the user already has 2 units and increases to 5, you’re adding 3 — not adding 5. Fire for the delta. Firing for the total quantity overstates add-to-cart value.

view_item The event that precedes add_to_cart — product detail page view.

remove_from_cart Tracking cart removals and quantity reductions.

view_cart Cart page view with full cart contents.

begin_checkout When the user initiates checkout — the next major funnel step.