Checkout used to be the one place themes could not reach. Shopify Plus checkout extensibility changed that — merchants can now add UI and logic at the step where revenue is decided.

Checkout extensibility in plain language

Extensibility means approved apps can render blocks inside checkout and thank-you / order status surfaces. You customize the experience without editing checkout.liquid or breaking Shopify's compliance boundaries.

UI extensions vs Shopify Functions

  • Checkout UI extensions control what shoppers see: gifts, upsells, banners, custom fields, accordions.
  • Shopify Functions control backend logic: discounts, payment customization, delivery rules, and validations.

Merchandising teams care most about UI extensions. Operations and finance should be in the room when Functions change pricing or payment behavior.

What you can merchandise in checkout now

Common Plus use cases we see:

  • Automatic gifts and customer-choice rewards
  • Checkout upsells tied to cart contents
  • Trust badges, payment icons, and campaign banners
  • Custom fields for B2B or compliance notes
  • Content on Thank You and Order Status pages (available on all stores for content widgets; Plus for full checkout UI)

Some features in apps are Plus-only for checkout UI; always confirm on the app listing before you plan a launch around a specific block.

Who should own checkout experiments

Treat checkout like a product surface with a small RACI:

  • Growth / retention owns offer logic and copy
  • Operations owns inventory for gift SKUs
  • Finance signs off on margin impact
  • Support documents what customers see when a promotion fails

Getting started without a six-month project

  1. Install a checkout extensibility app on a development or duplicate store.
  2. Ship one offer — a single threshold gift or one upsell.
  3. Measure completion rate and AOV for two weeks.
  4. Add trust content or payment tweaks only after baseline is stable.

Smart Checkout Widgets bundles gifting, discounts, upsells, and trust content so you are not stitching five single-purpose apps together.

Related guides

Go deeper on specific tactics:

Frequently asked questions

What is Shopify Plus checkout extensibility?

It allows approved apps to add UI and logic inside checkout and related surfaces using checkout UI extensions and Shopify Functions, without editing checkout.liquid.

What is the difference between checkout UI extensions and Shopify Functions?

UI extensions control what shoppers see. Functions control backend logic such as discounts, validations, and payment customization.

Install on Shopify All blog guides Back to homepage