> For the complete documentation index, see [llms.txt](https://docs.selvette.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.selvette.com/custom-sites/add-to-cart.md).

# Connect add to cart

Shopify stores use Selvette's native Shopify cart integration. A custom site must provide a small JavaScript hook so Selvette can add the tried-on product or AR shade to your cart.

Define `window.__tryonAddToCart` before the shopper uses Add to cart:

```html
<script>
  window.__tryonAddToCart = async ({ productRef, variantRef, qty }) => {
    await myCart.add(productRef, {
      variant: variantRef,
      qty,
    });
    return true;
  };
</script>
```

The hook receives:

* `productRef` — the value from `data-tryon-product`;
* `variantRef` — the selected shade or variant when available; and
* `qty` — currently `1`.

## Report success honestly

* Return `true` after your cart confirms the add.
* Return `false` if the cart rejects it.
* Throw an error if your cart request fails.

Selvette supports asynchronous hooks and waits for the result. Without this hook, a non-Shopify site reports the add as failed instead of showing a false success message.

Next: [Test a custom-site installation](/custom-sites/test-your-installation.md)


---

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