Carts are smart buyer assistants that contain the merchandise that a buyer intends to purchase and information about the buyer.
This guide introduces carts within the context of the buying journey, ways that you can extend a cart's functionality, and some considerations before you get started with building carts.
## How it works
The following components form a part of every buying journey:
- A **storefront** is where merchants tell their brand story, and where customers browse available products.
- A **cart** is where customers add products that they're interested in buying, and remove products that they no longer want to buy. A customer might visit their cart multiple times to renegotiate with themselves before they make a final purchase.
- A **checkout** is where a customer makes their final decision to purchase products, and completes a transaction.
## Benefits
The carts that most buyers encounter are simple baskets that are only used to collect products. They lack functionality and context, and typically lead to buyer frustration at checkout.
Shopify-powered carts provide the following benefits:
- Display accurate and personalized discounts, tax, and shipping estimates.
- Provide price transparency in real time, and at each new step of the purchase journey.
- Run brand-provided custom business logic.
- Shortcut buyers through checkout by providing known buyer preferences, such as payment methods or shipping details.
- Offer fast and predictable performance no matter the size of the store or the sale.
## Extensibility options
Many merchants have unique business requirements. You can extend the functionality of a cart, while ensuring it's performant, reliable, and scalable in checkout, in the following ways:
| Feature | Description | Example use cases |
| ------- | ----------- | -------- |
| [Shopify Functions](/docs/apps/build/functions) | Extend and customize Shopify's default logic and provide consistency throughout the buyer journey.| Create a custom validation function that can be executed by Shopify on every cart update to do the following:
Validate or limit the number of items a buyer can add to their cart.
Validate an address or check for a PO box.
|
| [Metafields](/docs/storefronts/headless/building-with-the-storefront-api/cart/manage#step-4-set-metafields-on-a-cart) | Create metafields to extend the cart schema with custom values and logic at checkout. | Attach custom structured metadata on a cart, and read it from a checkout extension to deliver a customized end-to-end buyer experience. |
| [Preferences](/docs/storefronts/headless/building-with-the-storefront-api/cart/manage#step-5-update-customer-information-and-customer-preferences-for-guest-checkout-journeys) | Set customer preferences to provide a personalized cart and checkout experience. | Provide a list of preferred delivery addresses to accelerate the checkout flow, and best optimize conversion. |
## International pricing
Carts offer [contextual experiences](/docs/storefronts/headless/building-with-the-storefront-api/markets/international-pricing#create-a-cart) based on location, language, and pricing. You can query international prices for products and orders, and explicitly set the context of a cart.
Users can configure the prices of products on a per country basis in their Shopify admin. For example, a storefront might have default prices for products set in USD, and price adjustments configured for Canada (CAD), Australia (AUD), and France (EUR).
The following diagram shows the different prices of the same product based on customer location:
## Speed and scale
Shopify's cart functionality is built on the same infrastructure as our storefronts. Carts are deployed globally and deliver a low-latency experience to buyers around the world.
Carts don't have any global API rate limits. This means that merchants can confidently launch their biggest flash sale, or absorb an unexpected wave of buyers.
> Note:
> Shopify continues to optimize every aspect of cart execution, including delivering reliable sub-100 millisecond response times for every cart operation.
## Developer tools and resources
Explore the following developer tools and resources to learn more about working with carts.
## Product Roadmap
> Note:
> This roadmap is being shared for informational purposes and is subject to change. Share your feedback on what future features you’d like to see in our [community discussion board](https://github.com/Shopify/storefront-api-feedback/discussions).
| Feature | Release Target |
|---|---|
| [Cart API Migration Guide](/docs/storefronts/headless/building-with-the-storefront-api/cart/migrate-to-cart-api) | 2024-04 |
| Append Gift Card to Cart | 2024-07 |
| Query and Set Carrier Calculated Shipping Rates | 2024-07 |
| Support Asynchronous Calls with `@defer` Directive | 2024-07 |
| `Cart.buyerIdentity` Authentication Carried Through to Checkout | 2024-07 |
| Support for Native Wallets (Apple Pay, Google Pay) in Mobile Apps on Cart | 2024-07 |
## Limitations and considerations
- The cart is subject to the [same throttling restrictions](/docs/api/usage/rate-limits#storefront-api-rate-limits) as the Storefront API.
- The cart supports a maximum of 500 line items.
- A shop or customer can create an unlimited number of carts.
- Unused and abandoned carts automatically expire within 10 days of creation.
- Shopify automatically deletes the cart when the customer completes their checkout.
- Shopify Plus [bot protection](https://help.shopify.com/manual/checkout-settings/bot-protection) is available for cart.
## Next steps
- Learn how to [create and update a cart](/docs/storefronts/headless/building-with-the-storefront-api/cart/manage) in Shopify with the Storefront API.
- Learn how to [migrate to the Cart API](/docs/storefronts/headless/building-with-the-storefront-api/cart/migrate-to-cart-api)
