Purchase combination rules control how items may be grouped in a cart. Three templates are available: Choose one permits one member of a target group, Shared limit caps the group's combined quantity, and Buy together requires items in a second group when a trigger group is present. For a separate cap on each product, use product limits.
Create a combination rule
- Open Purchase combination rules (
/combinations) from the app's primary navigation, create a rule, and enter a Rule name. - Select a Rule type. Its type is locked after creation; create a new rule for another template.
- Under Groups / targets, define the scope using the available all-products, product, collection, or variant choices. Buy together uses separate Trigger group and Required group targets.
- Configure the template. For Choose one, select Product or Variant as the selection unit and set the chosen member's maximum quantity (
-1means no quantity cap). For Shared limit, enter a Maximum shared limit greater than zero. For Buy together, choose Presence only, fixed 1:1 Same quantity, or a custom Ratio. - Set buyer conditions, dates, messages, and Enforcement timing as needed. Enable the rule's Enable checkout validation, save it, and save its message under Translation.
Passing and failing carts
| Template | Configuration | Passes | Fails |
|---|---|---|---|
| Choose one | A and B; Product selection unit; maximum two units of the chosen member | Two A units | One A plus one B; or three A units |
| Shared limit | A and B share a cap of three units | Two A plus one B | Two A plus two B, totaling four |
| Buy together | A is Trigger, B is Required; Same quantity uses fixed 1:1 | Two A plus two B | Two A plus one B |
For Choose one, a maximum of
-1 removes only the quantity cap on the selected member; it still does not permit two different group members. Presence only requires at least one Required item when Trigger is present. Ratio calculates a required quantity from the configured trigger and required units, rounding the target up. Review the editor preview and verify with a real cart. Exclusive purchase covers a single target that must not share a cart with other items.After saving, test each passing and failing cart and check the store's checkout validation status.
Keep going
Use a test product or cart to check the outcome before applying this setup across your store.
All guides