> ## Documentation Index > Fetch the complete documentation index at: https://docs.fourthwall.com/llms.txt > Use this file to discover all available pages before exploring further. # Change Cart Quantity ## OpenAPI ````yaml /openapi/storefront.json POST /v1/carts/{cartId}/change openapi: 3.1.0 info: title: Fourthwall APIs description: Service used for management of orders, carts, and payments. termsOfService: https://fourthwall.com/terms-of-service contact: name: Backend team url: https://fourthwall.com email: backend@fourthwall.com version: unspecified servers: - url: https://storefront-api.fourthwall.com description: Production server security: [] externalDocs: description: OpenAPI documentation url: https://docs.fourthwall.com paths: /v1/carts/{cartId}/change: post: tags: - headless_carts summary: Change cart items quantity operationId: change-cart-quantity parameters: - name: storefront_token in: query required: true schema: type: string example: ptkn_xxxxxxxxxxxxxxxxxx - name: cartId in: path required: true schema: type: string - name: currency in: query required: false schema: type: string enum: - USD - EUR - CAD - GBP - AUD - NZD - SEK - NOK - DKK - PLN - INR - JPY - MYR - SGD - MXN - BRL - CHF requestBody: content: application/json: schema: $ref: >- #/components/schemas/com.fourthwall.app.headless.endpoint.HeadlessCart.XRequest required: true responses: '200': description: OK content: application/json: schema: $ref: '#/components/schemas/com.fourthwall.app.headless.model.CartV1' '400': description: >- Possible errors: `CART_FORBIDDEN_MEMBERS_ONLY_OFFERS_ERROR`, `CART_INCOMPLETE_BUNDLE_ERROR`, `CART_ITEM_NOT_FOUND_FOR_SHOP_ERROR`, `CART_OFFER_NOT_AVAILABLE`, `CART_OFFER_NOT_PURCHASABLE_ERROR`, `CART_QUANTITY_TOO_HIGH` content: application/json: examples: cart-forbidden-members-only-offers-error: value: code: CART_FORBIDDEN_MEMBERS_ONLY_OFFERS_ERROR offerIds: cart-incomplete-bundle-error: value: code: CART_INCOMPLETE_BUNDLE_ERROR bundleId: details: cart-item-not-found-for-shop-error: value: code: CART_ITEM_NOT_FOUND_FOR_SHOP_ERROR shopId: variantId: cart-offer-not-available: value: code: CART_OFFER_NOT_AVAILABLE variantId: cart-offer-not-purchasable-error: value: code: CART_OFFER_NOT_PURCHASABLE_ERROR variantId: cart-quantity-too-high: value: code: CART_QUANTITY_TOO_HIGH variantId: quantity: '404': description: >- Possible errors: `CART_NOT_FOUND`, `CART_OFFER_NOT_FOUND`, `OFFER_VARIANT_NOT_FOUND_ERROR` content: application/json: examples: cart-not-found: value: code: CART_NOT_FOUND cartId: cart-offer-not-found: value: code: CART_OFFER_NOT_FOUND variantId: groupedId: offer-variant-not-found-error: value: code: OFFER_VARIANT_NOT_FOUND_ERROR offerVariantId: externalDocs: url: >- https://docs.fourthwall.com/api-reference/storefront/carts/change-cart-quantity components: schemas: com.fourthwall.app.headless.endpoint.HeadlessCart.XRequest: type: object properties: items: type: array items: $ref: >- #/components/schemas/com.fourthwall.app.headless.endpoint.HeadlessCart.RequestItem metadata: type: object additionalProperties: type: string description: >- Custom metadata key-value pairs. Max 10 keys, keys must be alphanumeric with underscores, max 256 chars per key, max 512 bytes per value, max 2KB total. example: asset_id: abc123 campaign: summer_2026 required: - items title: X Request com.fourthwall.app.headless.model.CartV1: type: object properties: id: type: string items: type: array items: $ref: >- #/components/schemas/com.fourthwall.app.headless.model.CartV1.CartItemV1 metadata: type: object additionalProperties: type: string required: - id - items title: Cart com.fourthwall.app.headless.endpoint.HeadlessCart.RequestItem: type: object properties: variantId: type: string format: uuid example: 000009c2-0c75-0024-0000-09c20c750024 quantity: type: integer format: int32 example: 1 maximum: 1000 minimum: 0 required: - quantity - variantId title: Request Item com.fourthwall.app.headless.model.CartV1.CartItemV1: type: object properties: variant: $ref: >- #/components/schemas/com.fourthwall.app.headless.model.CartProductVariantV1 quantity: type: integer format: int32 groupedBy: oneOf: - $ref: >- #/components/schemas/com.fourthwall.app.headless.model.CartItemGroupedByV1.Bundle required: - quantity - variant title: Cart Item com.fourthwall.app.headless.model.CartProductVariantV1: type: object properties: id: type: string name: type: string sku: type: string unitPrice: $ref: '#/components/schemas/Money' compareAtPrice: $ref: '#/components/schemas/Money' attributes: $ref: >- #/components/schemas/com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Attributes stock: oneOf: - $ref: >- #/components/schemas/com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Stock.Limited - $ref: >- #/components/schemas/com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Stock.Unlimited weight: $ref: >- #/components/schemas/com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Weight dimensions: $ref: >- #/components/schemas/com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Dimensions images: type: array items: $ref: '#/components/schemas/com.fourthwall.openapi.model.Image' product: $ref: '#/components/schemas/com.fourthwall.app.headless.model.ProductStubV1' required: - attributes - dimensions - id - images - name - product - sku - stock - unitPrice - weight title: Cart Product Variant com.fourthwall.app.headless.model.CartItemGroupedByV1.Bundle: allOf: - $ref: >- #/components/schemas/com.fourthwall.app.headless.model.CartItemGroupedByV1 - type: object properties: bundleId: type: string groupedId: type: string required: - bundleId - groupedId title: Bundle Money: type: object properties: value: type: number example: 10 minimum: 0 currency: type: string example: USD required: - currency - value title: Money com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Attributes: type: object properties: description: type: string example: Black, L color: $ref: >- #/components/schemas/com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Attributes.Color size: $ref: >- #/components/schemas/com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Attributes.Size required: - description title: Attributes com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Stock.Limited: allOf: - $ref: >- #/components/schemas/com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Stock - type: object properties: inStock: type: integer format: int32 example: 5 - type: object properties: type: type: string const: LIMITED required: - inStock title: Limited com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Stock.Unlimited: allOf: - $ref: >- #/components/schemas/com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Stock - type: object properties: type: type: string const: UNLIMITED title: Unlimited com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Weight: type: object properties: value: type: number example: '1.0' unit: type: string example: kg required: - unit - value title: Weight com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Dimensions: type: object properties: length: type: number example: '1.0' width: type: number example: '2.0' height: type: number example: '3.0' unit: type: string example: cm required: - height - length - unit - width title: Dimensions com.fourthwall.openapi.model.Image: type: object properties: id: type: string example: 00aa4abd-5778-4199-8161-0b49b2f212e5 url: type: string example: https://fourthwall.com/image.png width: type: integer format: int32 description: The original width of the image in pixels. example: 800 height: type: integer format: int32 description: The original height of the image in pixels. example: 600 transformedUrl: type: string description: >- Transformed URL with applied image processing (e.g., resizing, optimization) example: https://fourthwall.com/image.png required: - height - id - transformedUrl - url - width title: Image com.fourthwall.app.headless.model.ProductStubV1: type: object properties: id: type: string name: type: string slug: type: string required: - id - name - slug title: Product Stub com.fourthwall.app.headless.model.CartItemGroupedByV1: discriminator: propertyName: type properties: type: type: string required: - type title: Cart Item Grouped By com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Attributes.Color: type: object properties: name: type: string example: Black swatch: type: string example: '#000000' required: - name - swatch title: Color com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Attributes.Size: type: object properties: name: type: string example: L required: - name title: Size com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Stock: discriminator: propertyName: type mapping: UNLIMITED: $ref: >- #/components/schemas/com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Stock.Unlimited LIMITED: $ref: >- #/components/schemas/com.fourthwall.openapi.model.OfferAbstractV1.OfferVariantAbstractV1.Stock.Limited properties: type: type: string required: - type title: Stock ````