Adding a Custom Field to the Shopkeeper Cart Form

Sometimes a store needs one extra field in the cart that does not belong to the product itself. Examples include engraving text, delivery notes, a company reference, or another buyer-provided value that should travel with the order.

The key distinction

This is not a product field. It is an order-input field. That means it belongs to the cart or checkout form rather than to the resource or product data model.

Implementation pattern

• add the input to the cart or checkout form markup
• make sure the submitted value is preserved through validation and cart updates
• include it in the email or order processing template
• store it in the order record if the project keeps structured order data

Why teams get stuck here

Many commerce instructions focus on product parameters, not on arbitrary fields attached to the cart session or final order. Once you separate those two concepts, the implementation becomes much clearer.

The safest approach is to treat the value as order metadata and keep it out of the product model entirely.