Shopify Checkout Customization

Any logic your store was running through Scripts for discounts, shipping, or payment methods is now inactive. The migration path is Shopify Functions, which handles the same logic types server-side using WebAssembly. We can audit your Scripts, map each one to its Functions equivalent, and build and test the replacements. If you are not sure what Scripts you had running, we can start with an audit of your checkout behaviour to identify what is now missing.

Checkout Components are the composable building blocks that define the checkout's structure and layout, replacing checkout.liquid as the supported UI customization path on Plus. Checkout UI Extensions are the mechanism for adding custom content, fields, banners, and blocks within those components. In practice: Components define what the checkout looks like at a structural level; Extensions add your specific customizations within that structure. Both require Shopify Plus.

Shopify Functions cover all the major Scripts use cases: custom discount logic, shipping rate calculation, payment method filtering, and order routing. Functions run server-side compiled to WebAssembly, which is more reliable and performant than Scripts were. Some very bespoke Scripts logic may require rethinking the approach when mapping to Functions, which is why we start with a thorough audit before writing any replacement code.

Shopify has set an October 1, 2026 deadline [verify] for migrating checkout and customer-account extensions to use Polaris web components. If you have existing Checkout UI Extensions built before this requirement, they will need to be updated. We track this as part of any checkout engagement and flag it explicitly if your extensions are affected.

It can in both directions. Well-placed custom fields, trust signals, and upsell blocks built through Checkout Components and Extensions can improve conversion. Poorly implemented customizations that slow the checkout, add friction, or confuse buyers reduce it. We pair checkout builds with a conversion review so every element added has a clear rationale.

Checkout-specific A/B testing is not covered by Shopify's native Rollouts feature, which handles theme and customer-account tests. For checkout experiments, dedicated tools like Shoplift or Convert are required. We note this distinction because it affects how you plan: build the checkout correctly first, then layer testing on top with a specialist tool.