How to Upsell Inside the Cart on Squarespace (Plugin Guide)
The cart page is one of the highest-converting places to show upsell offers in your entire Squarespace store. The customer has already decided to buy — they're reviewing their order, not still evaluating whether to purchase. A well-placed, relevant offer at this moment converts at higher rates than the same offer shown earlier in the journey.
Here's how to add upsell offers inside the cart on Squarespace — both on the cart page and inside the slide-out cart drawer.
Why Cart-Stage Upsells Work So Well
There's a simple psychological reason: commitment. A customer who has added something to their cart has already crossed the mental threshold of "I'm buying something." Adding one more relevant item feels like a natural extension of a decision they've already made — not a new decision from scratch.
This is why cart upsells consistently outperform product page upsells in conversion rate studies. The customer is further along in the buying process. Their resistance is lower. Their receptivity is higher.
Two Types of Cart on Squarespace
Squarespace has two cart experiences:
The cart page: A dedicated page showing all cart items, the order summary, and the checkout button. Customers navigate here by clicking the cart icon or being redirected after adding a product.
The slide-out cart drawer: A panel that slides in from the side without leaving the current page. This requires a plugin — Squarespace doesn't have a native drawer. UpsellGrow includes one.
Both are opportunities for upsell offers. UpsellGrow supports both.
Upselling on the Cart Page
UpsellGrow adds offer widgets to the Squarespace cart page in five positions:
- Top of cart — above all items, high visibility
- Left of cart — alongside the items list
- Right of cart — beside the order summary (consistently high-converting)
- Bottom of cart — below all items
- Popup on checkout click — fires when the customer clicks Checkout
Right of cart is the strongest position for most stores — it sits next to where the customer is already looking (the order total and checkout button) and feels natural rather than intrusive.
Upselling Inside the Slide-Out Cart Drawer
UpsellGrow's slide-out cart drawer supports three offer positions:
- Inside drawer, above checkout — the last touchpoint before payment
- Inside drawer, below items — seen as the customer reviews their cart
- Popup on checkout click — fires as they proceed to checkout
Cart Trigger Behaviour
When multiple products are in a customer's cart, you need to decide which one determines which offer fires. UpsellGrow's cart trigger behaviour setting (available per offer in the Rules tab) lets you choose:
Last product added (default): The most recently added item triggers the offer. Most relevant to the customer's immediate action.
Highest value product: The most expensive item in the cart determines which offer shows. Good for stores with a clear premium product.
Highest priority offer: The system ignores which product triggered it and fires the highest-ranked qualifying offer regardless of cart composition.
What Offers Work Best in the Cart
Bundle offers perform particularly well on the cart page and in the drawer. The customer can see their current cart total and evaluate the math — "add these two items for $X and save $Y." The context makes the value proposition easy to understand.
Cross-sells work well if the suggested product is tightly relevant to what's already in the cart. A generic suggestion on the cart page is worse than no suggestion — it looks like an afterthought.
FBT offers — showing what other customers who bought the same product also bought — carry social proof that works well at the cart stage.
Setting It Up
In UpsellGrow, create a new offer, select "Cart Page" or "Slide-out Cart" as the location, configure the offer type and products, choose the position, set any conditions, and publish. The offer goes live immediately.
Ready to Start Earning More From Every Order?
UpsellGrow adds upsells, cross-sells, bundles, and frequently bought together offers to your Squarespace store — across 5 pages and 19 positions. No coding. Setup takes minutes.