---
title: BaseCartLine - Storefront API
description: >
  Defines the shared fields for items in a shopping cart. Implemented by
  [`CartLine`](/docs/api/storefront/2026-01/objects/CartLine) for individual
  merchandise and
  [`ComponentizableCartLine`](/docs/api/storefront/2026-01/objects/ComponentizableCartLine)
  for grouped merchandise like bundles.


  Each implementation includes the merchandise being purchased, quantity, cost
  breakdown, applied discounts, custom attributes, and any associated
  [`SellingPlan`](/docs/api/storefront/2026-01/objects/SellingPlan).
api_version: 2026-01
api_name: storefront
type: interface
api_type: graphql
source_url:
  html: 'https://shopify.dev/docs/api/storefront/latest/interfaces/BaseCartLine'
  md: 'https://shopify.dev/docs/api/storefront/latest/interfaces/BaseCartLine.md'
---

# Base​Cart​Line

interface

Defines the shared fields for items in a shopping cart. Implemented by [`CartLine`](https://shopify.dev/docs/api/storefront/2026-01/objects/CartLine) for individual merchandise and [`ComponentizableCartLine`](https://shopify.dev/docs/api/storefront/2026-01/objects/ComponentizableCartLine) for grouped merchandise like bundles.

Each implementation includes the merchandise being purchased, quantity, cost breakdown, applied discounts, custom attributes, and any associated [`SellingPlan`](https://shopify.dev/docs/api/storefront/2026-01/objects/SellingPlan).

## Fields

* attribute

  [Attribute](https://shopify.dev/docs/api/storefront/latest/objects/Attribute)

  An attribute associated with the cart line.

  * key

    [String!](https://shopify.dev/docs/api/storefront/latest/scalars/String)

    required

    ### Arguments

    The key of the attribute.

  ***

* attributes

  [\[Attribute!\]!](https://shopify.dev/docs/api/storefront/latest/objects/Attribute)

  non-null

  The attributes associated with the cart line. Attributes are represented as key-value pairs.

* cost

  [Cart​Line​Cost!](https://shopify.dev/docs/api/storefront/latest/objects/CartLineCost)

  non-null

  The cost of the merchandise that the buyer will pay for at checkout. The costs are subject to change and changes will be reflected at checkout.

* discount​Allocations

  [\[Cart​Discount​Allocation!\]!](https://shopify.dev/docs/api/storefront/latest/interfaces/CartDiscountAllocation)

  non-null

  The discounts that have been applied to the cart line.

* id

  [ID!](https://shopify.dev/docs/api/storefront/latest/scalars/ID)

  non-null

  A globally-unique ID.

* merchandise

  [Merchandise!](https://shopify.dev/docs/api/storefront/latest/unions/Merchandise)

  non-null

  The merchandise that the buyer intends to purchase.

* quantity

  [Int!](https://shopify.dev/docs/api/storefront/latest/scalars/Int)

  non-null

  The quantity of the merchandise that the customer intends to purchase.

* selling​Plan​Allocation

  [Selling​Plan​Allocation](https://shopify.dev/docs/api/storefront/latest/objects/SellingPlanAllocation)

  The selling plan associated with the cart line and the effect that each selling plan has on variants when they're purchased.

* estimated​Cost

  [Cart​Line​Estimated​Cost!](https://shopify.dev/docs/api/storefront/latest/objects/CartLineEstimatedCost)

  non-nullDeprecated

***

## Types implemented in

* [Cart​Line](https://shopify.dev/docs/api/storefront/latest/objects/CartLine)

  OBJECT

  An item in a customer's [`Cart`](https://shopify.dev/docs/api/storefront/2026-01/objects/Cart) representing a product variant they intend to purchase. Each cart line tracks the merchandise, quantity, cost breakdown, and any applied discounts.

  Cart lines can include custom attributes for additional information like gift wrapping requests, and can be associated with a [`SellingPlanAllocation`](https://shopify.dev/docs/api/storefront/2026-01/objects/SellingPlanAllocation) for purchase options like subscriptions, pre-orders, or try-before-you-buy. The [`instructions`](https://shopify.dev/docs/api/storefront/2026-01/objects/CartLine#field-CartLine.fields.instructions) field indicates whether the line can be removed or have its quantity updated.

  * attribute

    [Attribute](https://shopify.dev/docs/api/storefront/latest/objects/Attribute)

    An attribute associated with the cart line.

    * key

      [String!](https://shopify.dev/docs/api/storefront/latest/scalars/String)

      required

      ### Arguments

      The key of the attribute.

    ***

  * attributes

    [\[Attribute!\]!](https://shopify.dev/docs/api/storefront/latest/objects/Attribute)

    non-null

    The attributes associated with the cart line. Attributes are represented as key-value pairs.

  * cost

    [Cart​Line​Cost!](https://shopify.dev/docs/api/storefront/latest/objects/CartLineCost)

    non-null

    The cost of the merchandise that the buyer will pay for at checkout. The costs are subject to change and changes will be reflected at checkout.

  * discount​Allocations

    [\[Cart​Discount​Allocation!\]!](https://shopify.dev/docs/api/storefront/latest/interfaces/CartDiscountAllocation)

    non-null

    The discounts that have been applied to the cart line.

  * id

    [ID!](https://shopify.dev/docs/api/storefront/latest/scalars/ID)

    non-null

    A globally-unique ID.

  * instructions

    [Cart​Line​Instructions!](https://shopify.dev/docs/api/storefront/latest/objects/CartLineInstructions)

    non-null

    The instructions for the line item.

  * merchandise

    [Merchandise!](https://shopify.dev/docs/api/storefront/latest/unions/Merchandise)

    non-null

    The merchandise that the buyer intends to purchase.

  * parent​Relationship

    [Cart​Line​Parent​Relationship](https://shopify.dev/docs/api/storefront/latest/objects/CartLineParentRelationship)

    The parent of the line item.

  * quantity

    [Int!](https://shopify.dev/docs/api/storefront/latest/scalars/Int)

    non-null

    The quantity of the merchandise that the customer intends to purchase.

  * selling​Plan​Allocation

    [Selling​Plan​Allocation](https://shopify.dev/docs/api/storefront/latest/objects/SellingPlanAllocation)

    The selling plan associated with the cart line and the effect that each selling plan has on variants when they're purchased.

  * estimated​Cost

    [Cart​Line​Estimated​Cost!](https://shopify.dev/docs/api/storefront/latest/objects/CartLineEstimatedCost)

    non-nullDeprecated

* [Componentizable​Cart​Line](https://shopify.dev/docs/api/storefront/latest/objects/ComponentizableCartLine)

  OBJECT

  Represents information about the grouped merchandise in the cart.

  * attribute

    [Attribute](https://shopify.dev/docs/api/storefront/latest/objects/Attribute)

    An attribute associated with the cart line.

    * key

      [String!](https://shopify.dev/docs/api/storefront/latest/scalars/String)

      required

      ### Arguments

      The key of the attribute.

    ***

  * attributes

    [\[Attribute!\]!](https://shopify.dev/docs/api/storefront/latest/objects/Attribute)

    non-null

    The attributes associated with the cart line. Attributes are represented as key-value pairs.

  * cost

    [Cart​Line​Cost!](https://shopify.dev/docs/api/storefront/latest/objects/CartLineCost)

    non-null

    The cost of the merchandise that the buyer will pay for at checkout. The costs are subject to change and changes will be reflected at checkout.

  * discount​Allocations

    [\[Cart​Discount​Allocation!\]!](https://shopify.dev/docs/api/storefront/latest/interfaces/CartDiscountAllocation)

    non-null

    The discounts that have been applied to the cart line.

  * id

    [ID!](https://shopify.dev/docs/api/storefront/latest/scalars/ID)

    non-null

    A globally-unique ID.

  * line​Components

    [\[Cart​Line!\]!](https://shopify.dev/docs/api/storefront/latest/objects/CartLine)

    non-null

    The components of the line item.

  * merchandise

    [Merchandise!](https://shopify.dev/docs/api/storefront/latest/unions/Merchandise)

    non-null

    The merchandise that the buyer intends to purchase.

  * quantity

    [Int!](https://shopify.dev/docs/api/storefront/latest/scalars/Int)

    non-null

    The quantity of the merchandise that the customer intends to purchase.

  * selling​Plan​Allocation

    [Selling​Plan​Allocation](https://shopify.dev/docs/api/storefront/latest/objects/SellingPlanAllocation)

    The selling plan associated with the cart line and the effect that each selling plan has on variants when they're purchased.

  * estimated​Cost

    [Cart​Line​Estimated​Cost!](https://shopify.dev/docs/api/storefront/latest/objects/CartLineEstimatedCost)

    non-nullDeprecated

***

##### Variables

```json
{
	"attribute": {
		"key": ""
	},
	"attributes": "",
	"cost": "",
	"discountAllocations": "",
	"estimatedCost": "",
	"id": "",
	"merchandise": "",
	"quantity": "",
	"sellingPlanAllocation": ""
}
```

##### Schema

```graphql
interface BaseCartLine {
  attribute: Attribute
  attributes: [Attribute!]!
  cost: CartLineCost!
  discountAllocations: [CartDiscountAllocation!]!
  estimatedCost: CartLineEstimatedCost!
  id: ID!
  merchandise: Merchandise!
  quantity: Int!
  sellingPlanAllocation: SellingPlanAllocation
}
```