# cartDiscountCodesUpdate

Updates discount codes for an existing cart.

## Authentication

> **Public Access**: Accessible with the public API key

## Mutation Structure

```graphql
mutation {
  cartDiscountCodesUpdate(id: String!, discountCodes: [String!]) {
    cart {
      # Cart fields
    }
    userErrors {
      # UserError fields
    }
  }
}
```

## Input Arguments

| Argument | Type | Required | Description |
|----------|------|----------|-------------|
| id | String! | Yes | The ID of the cart to update discount codes for |
| discountCodes | [String!] | No | A list of discount codes to apply to the cart |

## Return Type

[CartDiscountCodesUpdatePayload](/reference/storefront/v1/objects/cart-discount-codes-update-payload) - Payload returned by the cartDiscountCodesUpdate mutation. Contains an optional updated cart and a required list of user errors that occurred during the update.

## Example

```graphql
mutation {
  cartDiscountCodesUpdate(
    id: "eyJhbGciOiJIUzI1NiJ9..."
    discountCodes: ["SUMMER20", "FREESHIP"]
  ) {
    cart {
      id
      totalQuantity
    }
    userErrors {
      field
      message
    }
  }
}
```

## Related Types

- [CartDiscountCodesUpdatePayload](/reference/storefront/v1/objects/cart-discount-codes-update-payload)