Separate required customer outcomes from the implementation details of scripts, checkout.liquid or unsupported DOM changes.
Map each requirement to UI extensions, Functions, pixels or standard settings, then test discounts, delivery, payment and error states.
Content and platform references reviewed on .
Describe the rule before the old code
Inventory every checkout customization by the customer or operating purpose it serves. Separate a visual message, a pricing rule, a delivery restriction and a tracking event even if one legacy script handled them all. Each may belong to a different supported replacement surface.
Verify plan and target eligibility
Shopify’s availability table distinguishes information, shipping and payment UI extensions from thank-you, order-status and account extensions. It also distinguishes public apps using Functions from custom Function apps. Confirm the actual target, plan and app distribution before estimating a replacement or promising identical behaviour.
Build a state matrix for the store
List the customer types, markets, currencies, subscriptions and discount combinations that affect each rule. Include accelerated checkout where relevant. For a blocked purchase, define the message and the action that lets the customer recover. Test conflicting or missing configuration rather than only a cart that qualifies for everything.
Release with a checkout owner
Document the activated extension configuration, required app versions and the person authorized to change them. Verify post-purchase pages and tracking as part of the same customer journey. Keep a recovery plan appropriate to the supported system; an unsupported legacy customization is not a dependable fallback.
Checks for this implementation
- Map every legacy behaviour to a requirement and a supported replacement.
- Test eligible and ineligible carts with the store’s actual purchase models.
- Confirm configuration, event reporting and recovery ownership before activation.
Common mistake to avoid
Rebuilding legacy behavior one-for-one can carry old friction into a newer, more maintainable platform.
A safe migration preserves critical outcomes while reducing upgrade risk and unsupported checkout code.
Platform references
Continue with Checkout planning guide, or discuss the requirements for your store.
