Telling a customer about a minimum at checkout is late. Telling them on the cart page, while they are still shopping, usually just means they add another item.
Before you start
- The theme app embed enabled and the theme saved — see install.
Steps
1. Install Nex Validator
Search Nex Validator in the Shopify App Store, or use the button below. Approve the permissions and the app appears in your admin under Apps. There is a free trial, and it works on every Shopify plan.
2. Open the rule and enable Show message in cart page.
3. Save with Status set to Enabled.
4. Open your cart with a cart that breaks the rule and check the message appears.
When your theme needs a hint
Themes differ enormously in how they build carts and drawers. The app auto-detects the usual patterns and exposes overrides for the rest:
| Setting | Use when |
|---|---|
| Checkout Button Selector | Your checkout button is not being found |
| Error Container Selector | The message needs to render somewhere specific |
| Cart Total Selector | The total is not being read correctly |
| Exclude Selector | Something should be left alone — a Buy Now button, say |
| Drawer Watch Selector | Messages do not appear in the cart drawer |
Each appends to the defaults rather than replacing them, so adding one does not switch auto-detection off. Leave them empty on most themes.
Styling it
Text Color and Custom CSS control how the message looks. Custom CSS is the one to reach for if you want a background, border or padding to match your theme — the default is deliberately plain so it inherits rather than clashes.
Verify it worked
- Cart that breaks the rule → message appears on the cart page.
- Same in the cart drawer, if your theme has one. This is where most themes need the Drawer Watch Selector.
- Fix the cart → the message clears.
- Force through to checkout anyway → checkout still blocks.
Point 4 matters. The cart-page message is a courtesy; the checkout block is the enforcement. Confirm you still have the second one.
Cart limits behave slightly differently
Cart quantity and cart amount limits are handled specially on the cart page, so that enforcing them does not interfere with changing quantities in the cart. If you notice cart limits behaving less immediately than product limits there, that is why — and checkout enforcement is unaffected either way.