Checkout blocking stops an invalid order at checkout. Locking the quantity selector helps earlier by preventing customers from choosing an invalid quantity on the product page.
Before you start
Make sure you have:
- The Premium plan.
- The Nex Validator app embed enabled and the theme saved — see install.
- The product you want to control and the quantity rule you want to use. Example: Minimum Quantity = 5.
The three rule types
The quantity rule is stored on each product in one metafield called Checkout Rule (checkout_ninja.rule, type Multi-line text), written as a JSON value. Setup is covered step by step in Product bulk limit.
| Type | What it means | Example value |
|---|---|---|
min_quantity | Lowest quantity the customer can select | {"value":5,"type":"min_quantity"} → customer cannot select below 5 |
max_quantity | Highest quantity the customer can select | {"value":10,"type":"max_quantity"} → customer cannot select above 10 |
multiple_of | Customer must order in multiples of this number | {"value":6,"type":"multiple_of"} → 6, 12, 18, 24… |
Steps
1. Install Nex Validator
If Nex Validator is not installed yet, install it from the Shopify App Store and approve the required permissions. If it is already installed, skip to the next step.
2. Open the Shopify theme editor, enable the Nex Validator app embed, and click Save.
3. Open the product you want to control. Under Product metafields, find Checkout Rule and enter the JSON value. Example: for a minimum of 5, enter {"value":5,"type":"min_quantity"} and save the product.
4. Open or create a rule in Nex Validator and turn on Allow bulk limit.
5. Make sure the rule is Enabled, then save your changes.
Verify it worked
- Open the product on your storefront.
- Try selecting a quantity that breaks your metafield rule.
- Confirm that the quantity selector prevents the invalid quantity. For example, if Minimum Quantity = 5, confirm that customers cannot select a quantity below 5.
- Test checkout as well to confirm the order is blocked if the rule is broken.
If your theme does not respond
If the quantity selector is not working, first check that:
- The app embed is enabled and the theme is saved.
- The product has the correct metafield value.
- Allow bulk limit is enabled.
If all three are correct but the quantity selector still does not follow the rule, your Shopify theme may handle quantity selectors differently. Check the theme-related settings or contact support.