Frequently Asked Questions
Everything you need to know about server-side validation rules, Shopify Functions, and order protection.
How does CartShield differ from old theme script apps?
Legacy apps injected JavaScript into your theme (liquid files or cart drawers). Savvy buyers could easily bypass them by going directly to /checkout or using express buttons like Shop Pay, Apple Pay, or Google Pay. CartShield runs 100% on native Shopify Functions (purchase.validation.run) directly on Shopify's checkout servers. There is zero theme code, zero script tags, and zero possibility of bypassing the validation.
Does CartShield affect checkout page speed or Core Web Vitals?
No! CartShield compiles to WebAssembly (Wasm) and runs inside Shopify's global edge sandbox in under 5 milliseconds. It executes synchronously during checkout submission without making external HTTP API calls. Your checkout stays lightning fast with zero impact on conversion rates.
Can I block PO Boxes only for specific heavy freight items?
Yes. CartShield allows condition scoping: you can choose to apply PO Box restrictions store-wide, or restrict it only when the customer's cart contains products from specific collections (e.g. "Heavy Freight", "Hazardous Materials", "Oversized Furniture").
What is the "Add-on Sample Dependency" rule?
Many merchants offer $1-$5 sample kits, promotional swag, or replacement parts intended only as add-ons to real orders. Without validation, customers frequently order only the subsidized sample, costing the merchant high shipping fees. CartShield checks whether the cart contains required qualifying products; if not, checkout is blocked with an instructional message.
How does B2B / Wholesale Pack Multiple validation work?
If you ship wholesale goods in cases of 6, 12, or 24, shipping loose units ruins warehouse packaging efficiency. You configure a step multiple (e.g., multiple of 6). CartShield divides the item quantity by 6; if there is a remainder, it halts checkout and notifies the buyer: "Wholesale orders must be in case multiples of 6. Current quantity: 4."
Where does the error message appear to the customer?
Depending on the rule type, CartShield can anchor errors directly to the relevant input field (such as the Shipping Address line for PO Box violations) or display a prominent checkout banner at the top of the payment review step for cart-level issues (such as minimum spend thresholds).
Is CartShield compatible with non-Shopify Plus stores?
Shopify Checkout Validation Functions are supported across modern Shopify checkouts via Checkout Extensibility. If your plan supports Checkout Extensibility rules in your Shopify Admin (Settings → Checkout), CartShield is 100% plug-and-play.
What happens if I uninstall the app?
Because CartShield injects zero scripts into your theme, uninstalling the app leaves zero leftover code or theme corruption. Shopify automatically deactivates the function extension upon uninstall.