> ## 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.

# Cart Checkout Endpoint

> Full reference for /cart/checkout?products=... direct checkout links

Use this endpoint to send a shopper directly into Fourthwall checkout from a URL.
It is especially useful when you want to pass product variants directly (`products=...`) from ads, feeds, or custom links.

Base URL:

```text theme={null}
https://{shop_domain}/cart/checkout
```

Recommended direct-products example:

```text theme={null}
https://{shop_domain}/cart/checkout?products=11111111-1111-1111-1111-111111111111:1,22222222-2222-2222-2222-222222222222:2&currency=USD
```

If you already have a Storefront API cart, `cartId` is also supported:

```text theme={null}
https://{shop_domain}/cart/checkout?cartId=22222222-2222-2222-2222-222222222222&currency=USD
```

## Request

* Method: `GET`
* Path: `/cart/checkout`
* Intended use: Browser redirect links (ads, email, social, product feeds, etc.)
* Use the root path (`/cart/checkout`), not a locale-prefixed path.

## Query Parameters

| Param                                                     | Required | Description                                                                |
| --------------------------------------------------------- | -------- | -------------------------------------------------------------------------- |
| `products`                                                | No       | Comma-separated list of cart items in `variantId[:quantity]` format.       |
| `cartId`                                                  | No       | Existing cart ID to checkout. If present and valid, `products` is ignored. |
| `coupon`                                                  | No       | Promo code to apply.                                                       |
| `currency`                                                | No       | Checkout currency (for example `USD`).                                     |
| `cart_origin`                                             | No       | Cart origin metadata.                                                      |
| `utm_*`, `_ga`, `_fbp`, `_fbc`, `gclid`, `fbclid`, `FPID` | No       | Marketing params are captured and propagated in checkout metadata.         |

## `products` Format

Format:

```text theme={null}
products=variantId[:quantity],variantId[:quantity],...
```

Rules:

* `variantId` must be a variant UUID (not product/offer ID).
* `quantity` is optional; default is `1`.
* Invalid quantity values fall back to `1`.
* Entries with too many separators (like `id:1:extra`) are skipped.
* URL-encoded input is supported.
* If any entry has an invalid variant UUID, parsing fails and `products` becomes empty.

Examples:

```text theme={null}
?products=11111111-1111-1111-1111-111111111111
?products=11111111-1111-1111-1111-111111111111:2
?products=11111111-1111-1111-1111-111111111111:1,22222222-2222-2222-2222-222222222222:3
```

## Behavior

Checkout creation flow:

1. If `products` contains valid variant entries, the endpoint can create/update a cart from those products.
2. If `cartId` is provided and valid, checkout uses that cart and ignores `products`.
3. If both are unavailable (no valid `cartId` and no valid `products`), redirect goes to `/`.
4. On success, a checkout is created/updated and the shopper is redirected to `/checkout/{checkoutId}`.

Promo code precedence:

1. `coupon` query param
2. Manually-applied promo already on cart
3. Automatically applied promo code from a shared link

Currency precedence:

1. `currency` query param
2. Session currency
3. `USD`

## Response

This endpoint responds with redirects:

* Success: `303 See Other` -> `/checkout/{checkoutId}`
* Empty/invalid input: `303 See Other` -> `/`
* Exception path: `303 See Other` -> `/?error_message=...`

## Google Merchant Center Template

This endpoint supports the Google template pattern:

```text theme={null}
https://{shop_domain}/cart/checkout?products={id}:1
```

## Example Integration

Direct variant handoff (primary):

```javascript theme={null}
function redirectToDirectCheckout(shopDomain, variantId, quantity = 1, coupon) {
  const params = new URLSearchParams({
    products: `${variantId}:${quantity}`
  });

  if (coupon) params.set("coupon", coupon);

  window.location.href = `https://${shopDomain}/cart/checkout?${params.toString()}`;
}
```

Cart ID handoff (also supported):

```javascript theme={null}
function redirectCartToCheckout(shopDomain, cartId, currency = "USD") {
  const params = new URLSearchParams({
    cartId,
    currency
  });

  window.location.href = `https://${shopDomain}/cart/checkout?${params.toString()}`;
}
```