Shopify Checkout Extensibility: A Guide for After checkout.liquid and Scripts

Key takeaways

• checkout.liquid, additional scripts and Shopify Scripts are retired; Checkout Extensibility replaces them on every plan.
• Checkout UI extensions add content and fields, Shopify Functions change discount, delivery and payment logic, and web pixels handle tracking.
• Customising the information, shipping and payment steps needs Shopify Plus; the Thank you and Order status pages can be extended on every plan.
• Extensions are upgrade-safe: Shopify can improve checkout without breaking your customisations.
• Audit what your old checkout did, then rebuild only what still earns its place.

For years, Shopify Plus brands customised checkout by editing checkout.liquid, and ran discount and shipping logic with Shopify Scripts. Both are now retired. In their place is Checkout Extensibility: a set of upgrade-safe tools that work with Shop Pay and Shopify's one-page checkout. Here is what changed and how to rebuild your checkout properly.

The key checkout deadlines

• 13 August 2024: checkout.liquid stopped working for the information, shipping and payment steps on Shopify Plus.
• 28 August 2025: Shopify Plus stores' Thank you and Order status pages moved to Checkout Extensibility.
• 30 June 2026: Shopify Scripts stopped running. Discount, shipping and payment logic now runs on Shopify Functions.
• 26 August 2026: Thank you and Order status pages on all other plans were upgraded, removing additional scripts and script tags.

If your store was upgraded automatically, anything that relied on the old code — tracking, upsells, custom fields, gift messages — may have stopped silently. That is the first thing to check.

What is Shopify Checkout Extensibility?

• Checkout UI extensions: Components that add content and functionality at set points in checkout: upsells, trust messages, delivery instructions, custom fields and loyalty balances. They use Shopify's own components, so they stay fast and consistent.
• Shopify Functions: Server-side logic that replaces Shopify Scripts: custom discounts, delivery and payment method rules, cart validation and bundles. Functions run on Shopify's infrastructure.
• Web pixels: Customer events tracking that replaces additional scripts. Pixels run in a sandbox, which protects checkout performance and customer data.
• Branding: Colours, fonts, logos and layout, set in the checkout editor or through the Checkout Branding API.

What you can customise on each plan

• All plans: Branding in the checkout editor, app extensions on the Thank you and Order status pages, web pixels and Functions provided by public apps.
• Shopify Plus: Checkout UI extensions on the information, shipping and payment steps, and custom Shopify Functions in your own apps.

How to migrate your checkout customisations

1. Audit: List everything your old checkout did: scripts, tracking tags, custom fields, discount rules and app integrations. The customisation reports in your Shopify admin are a good starting point.
2. Decide: For each item, choose a public app, a custom extension or Function, or retire it. Many old customisations are no longer needed.
3. Rebuild tracking first: Move analytics and ad pixels to Customer Events and test conversions end to end; lost tracking is the most expensive silent failure.
4. Rebuild logic with Functions: Recreate tiered discounts, shipping rules and payment restrictions as Shopify Functions, and test them against real carts.
5. Build UI extensions: Add upsells, fields and messages as checkout UI extensions, placed in the checkout editor.
6. Test and monitor: Place test orders with every payment method, market and discount, then watch conversion rate and average order value after launch.

Why Checkout Extensibility is better

The old approach let you change anything, which also meant anything could break when Shopify updated checkout. Extensions and Functions are upgrade-safe, don't block the page as it loads and work with Shop Pay and one-page checkout. For most brands, the result is a faster checkout that needs far less maintenance.

Need help rebuilding your checkout? We build custom Shopify apps, checkout UI extensions and Shopify Functions, and handle Shopify Plus development end to end. Talk to us about your checkout.