📍 Bolt Help / Core Products / Checkout / Custom Cart Checkout / Set Up Cart-Based Product Add-Ons

Set Up Cart-Based Product Add-Ons

Integrate your own upsell engine with Bolt's Checkout to deliver product upsells to your shoppers as they check out, based on what is in their cart and more.

Cart-Based Product Add-Ons is currently available to participating Beta merchants.

Product Upsells are a powerful driver of Average Order Value (AOV) and enable merchants to make personalized recommendations to their shoppers based on what is currently in their cart, shopping history, and browsing history.


This feature is currently only available for Custom Carts.

Before You Start

Cart-Based Add-Ons require that you have the Enable cart based dynamic add-ons flag turned on for your merchant division. Reach out to your Bolt Integration Engineer or Customer Success Manager to enable this feature.

Additionally, you must specify the Update Cart URL for your merchant division. This can be communicated to your Bolt Integration Engineer or Customer Success Manager, as well. You must then implement the Update Cart URL in your code to allow the Add-Ons to be added to your cart using the cart.update endpoint in our Merchant Callback API.

If you already have non-Cart based Add-Ons enabled, as listed in our in our Product Add-Ons and Upsells documentation, then no changes need to be made to this endpoint.

Order Creation

To associate Add-Ons with the current cart, you must include the Add-Ons in the Cart JSON during order creation, as seen in the Order Creation endpoint.

Example of a Cart JSON that includes add_ons:

"cart": {
  "id": "4032665549291181",
  "displayId": "5913529137882847",
  "items": [
      "reference": "3",
      "image": "https://placeimg.com/30/30/animals/grayscale",
      "name": "Item3",
      "price": "$8.94",
      "desc": "Item3, the new gold standard for items",
      "sku": "SK-3",
      "quantity": 1
  "currency": "USD",
  "add_ons": [
 	 "name": "Add On 1",
	  "description": "An important add on",
	  "productId": "product_1",
	  "imageUrl": "https://picsum.photos/88/88",
        "productPageUrl": "https://bolt.com",
  	  "price": 199
 	  "name": "Add On 2",
	  "description": "Compliments Item 3",
	  "productId": "product_2",
	  "imageUrl": "https://picsum.photos/88/88",
        "productPageUrl": "https://bolt.com",
  	  "price": 249

That’s it! Nothing else needs to be done for your Add-Ons to appear in the checkout modal.

Cart-Based Add-Ons

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