Checkout rule actions reference

Rule settings

These fields sit above the actions on every rule.

Setting	What it does	Default
Title	Name for your reference, up to 30 characters. Buyers never see it.	Empty
Status	Active rules run in checkout. Draft rules don’t.	Draft
Condition Match Type	Only apply when All Conditions Pass, or Only apply when Any Condition Passes.	Any
Conditions	The conditions that trigger the rule. A rule with none always applies. Every condition.	None
Actions	What happens when the rule applies. At least one is needed for the rule to do anything.	None

Actions at a glance

Action	What the buyer sees	Needs block progress permission
Hide payment method	A payment method disappears from the payment step	No
Show Error Message	An error message, and they can’t continue	Yes
Modify Cart: Add Product	A product added to the order summary	No
Modify Cart: Set Product Quantity	A cart line’s quantity changes	No
Validate Via API	Nothing, unless your API returns errors or payment actions	Yes, for errors to block

“Block progress permission” means you’ve allowed the Rules Executor block to block checkout progress in Shopify’s checkout editor. How to add it.

Hide payment method

Hides payment methods by name while the rule matches.

Field	What it does	Default
Payment Method name contains	The text to match against payment method names. Pick from the list or type a name. Matching is “contains” and ignores case.	Empty

• Use one payment method per action. For several methods, add several Hide payment method actions.
• The hide is carried out by Checkout Ninja’s payment customization. When no hide rule matches, all methods show again.

Show Error Message

Shows an error and blocks the buyer from continuing while the rule matches. Guide.

Field	What it does	Default
Position	Where the message appears.	Empty
Message	The text shown to the buyer. Plain text.	Empty

Position options:

Option	Shown at
Top of the checkout	The top of the checkout page
Shipping Address 1	The first address line
Shipping Address 2	The second address line
First Name	The shipping first name
Last Name	The shipping last name
Email	The email field
Phone	The phone field

If a message set to Email or Phone doesn’t appear by the field, switch it to Top of the checkout. It blocks checkout either way.

Modify Cart - Add Product / Update Product Quantity

Changes the cart. Choose one of two modes. Guide.

Add Product

Field	What it does	Default
Product Variant	The variant to add. If the selection has several variants, the first is used.	Empty
Quantity	How many to add. Empty or invalid values add 1.	Empty (adds 1)
Prevent adding duplicate products	Skips the add when the variant is already in the cart.	On
Limit total quantity in cart	Turns on a cart quantity cap for this variant. Shows Quantity limit enabled or No quantity limit.	Off
Maximum quantity allowed	With the limit on, the product is only added while its cart quantity is below this number.	Empty

Set Product Quantity

Field	What it does	Default
Product	The product and variant whose cart line to change. The variant must already be in the cart.	Empty
Quantity	The quantity to set. Empty, 0 or invalid values set 1.	Empty (sets 1)

Validate Via API

Sends checkout data to your endpoint and applies its response. Full contract.

Field	What it does	Default
API URL	Your HTTPS endpoint. Called with POST and a JSON body.	Empty
API Headers	Shown in the editor but not currently sent with the request.	Empty
Input Query	GraphQL-style list of fields to send, for example { deliveryAddress { zip } }. Empty sends all checkout data.	Empty

• The request carries Content-Type: application/json and X-checkout-session-token.
• The response must include an actions array. Entries in an optional errors array block checkout.
• Responses are cached for 5 minutes per URL and identical data.

How rules run

• The Rules Executor loads your active rules when the checkout opens. It reads 10 rules from your store, drafts included, then drops drafts.
• It re-evaluates every rule whenever the checkout changes, such as the cart, address, email, discounts or selected payment option, after a 300 ms pause.
• While it evaluates, it holds checkout progress for that moment, if you’ve allowed it to block progress.
• Actions from all matching rules are collected and applied together.