Shield Mode publishes your enabled protection rules into Shopify’s cart validation Function. During checkout, Shopify evaluates the Function and can return errors that stop the buyer from completing the order.
Requirements
- A plan that includes Shield / enforcement
- At least one protection rule enabled and saved
- Protection sync showing as synced (not pending/failed)
- CheckoutGuard validation enabled under Checkout rules
Fail-open behavior
CheckoutGuard is designed so unexpected Function failures do not indiscriminately brick every checkout. Treat Shield as a configurable control layer — not a guarantee that every abusive attempt is blocked.
Before you go live with Shield
- Start with Monitor and understand your traffic.
- Enable one conservative rule at a time.
- Run a blocked checkout test.
- Watch for legitimate buyers hitting the rule; tune thresholds.