Why Checkout Extensibility Matters
The checkout is the highest-stakes page on your store. Shopify Plus Checkout Extensibility replaces the deprecated checkout.liquid with a stable, upgrade-safe framework for customising the checkout experience. Our development team builds checkout extensions that increase conversion rates and average order values.
Checkout UI Extensions
What You Can Build
UI extensions let you add custom elements to the checkout page — loyalty point displays, delivery date pickers, gift message fields, trust badges, upsell widgets, and custom banners. Extensions render within Shopify’s checkout using a sandboxed React-based framework.
Extension Points
Shopify provides specific extension points where your UI can appear: before and after the shipping method, before and after payment, order summary sidebar, and the thank-you page. Each point accepts different types of content and interactions.
Building Extensions
Use the Shopify CLI to scaffold a checkout extension project. Write components using Shopify’s UI library (not standard HTML/CSS) for consistent, accessible rendering. Extensions access checkout data through APIs for customer info, cart contents, and shipping details.
Shopify Functions
Discount Functions
Create custom discount logic that runs on Shopify’s infrastructure. Build BOGO offers, tiered volume discounts, conditional discounts based on customer tags, and time-limited flash sale pricing. Functions execute in milliseconds with no external API calls.
Shipping Functions
Customise shipping rate calculations — hide rates based on cart contents, rename shipping methods, add surcharges for specific products, or offer free shipping for loyalty members. More reliable than third-party carrier apps.
Payment Functions
Filter available payment methods based on cart value, customer location, or product type. Hide COD for high-value orders, show specific gateways for B2B customers, or enforce minimum orders for certain payment types.
Post-Purchase Extensions
Add one-click upsells between payment and the thank-you page. Customers can add products without re-entering payment details. This frictionless upsell typically increases AOV by 10-15%. A powerful CRO technique exclusive to Shopify Plus.
Web Pixel Extensions
Deploy custom tracking pixels that survive ad blockers by running in a sandboxed environment. Track checkout events for analytics, advertising platforms, and attribution tools with improved accuracy compared to client-side scripts.
Best Practices
- Keep extensions lightweight — every millisecond counts at checkout
- Test extensively across devices and payment methods
- Follow Shopify’s UX guidelines for checkout consistency
- Monitor conversion rates before and after deploying extensions
- Use feature flags to A/B test new checkout features
Need checkout customisation? Our Plus specialists build extensions that measurably improve conversions.
