Complete guide to Shopify checkout extensions (2026)

Shopify deprecated checkout.liquid in 2024 and replaced it with Checkout Extensibility. If you’ve heard terms like “checkout UI extensions,” “Shopify Functions,” or “checkout editor” and wondered what they actually mean—this guide explains the whole system.

The short version: Checkout Extensibility is how you customize checkout on Shopify now. Some features work on all plans. The powerful ones require Plus.

About this guide: Dash Checkout builds checkout and order management tools for Shopify. This guide covers the extensibility system from a merchant perspective—what you can do, what you need, and when apps versus custom development makes sense.

What checkout extensibility actually is

Checkout Extensibility is Shopify’s framework for customizing checkout without editing code directly. It has three main components:

Together, these replace the old checkout.liquid file that Plus merchants could edit directly. The new system is more structured, more secure, and app-based rather than code-based.

What standard plans can customize

If you’re on Basic, Grow, or Advanced, your checkout customization options are limited:

You can change:

• Logo and favicon
• Colors (background, buttons, text)
• Fonts
• Corner radius of inputs and buttons

You cannot:

• Add custom fields
• Modify checkout layout
• Insert upsells during checkout
• Add trust badges or custom content
• Run validation rules
• Customize shipping or payment steps

The thank-you page and order status page are more flexible—you can add app blocks there on all plans. But the checkout flow itself (information, shipping, payment) is locked.

What Plus unlocks

Shopify Plus gives you full access to Checkout Extensibility:

Checkout Editor

A visual drag-and-drop interface for customizing checkout. You can:

• Rearrange checkout sections
• Add, remove, and reorder blocks
• Configure app extensions without code
• Create checkout profiles for different scenarios (different checkouts for different markets or customer segments)

Checkout UI Extensions

Apps can add functionality at specific points in checkout:

Information step:

• Custom fields (delivery instructions, gift messages)
• Age verification checkboxes
• Terms acceptance with custom text

Shipping step:

• Delivery date pickers
• Shipping insurance options
• In-store pickup selectors

Payment step:

• Trust badges and security messaging
• Loyalty point displays
• Subscription toggles

Order summary:

• Cross-sell and upsell offers
• Gift wrap options
• Donation add-ons

Post-purchase:

• One-click upsells after checkout completes
• Survey collection
• App promotions

Shopify Functions

Server-side logic that runs on Shopify’s infrastructure. Functions handle:

Discounts:

• Custom discount logic beyond native capabilities
• Conditional discounts based on cart composition
• Tiered discounts with complex rules

Shipping:

• Custom shipping rate calculations
• Carrier filtering based on product attributes
• Delivery date estimation

Payment:

• Payment method filtering (hide certain options)
• Payment customization based on order value

Validation:

• Cart validation before checkout
• Order blocking when rules aren’t met
• Custom business rule enforcement

Functions run in WebAssembly for near-native speed—no external API latency.

Checkout UI Extensions vs Shopify Functions

These two systems work together but do different things:

A checkout upsell needs both: a UI extension to display the offer, and potentially a function to calculate the discounted price.

How merchants use checkout extensions

You don’t need to build extensions yourself. Apps from the Shopify App Store wrap checkout extensibility in merchant-friendly interfaces.

Common app categories

Upsells and cross-sells: Apps like AfterSell, ReConvert, and Checkout Wiz add upsell offers during and after checkout. They use checkout UI extensions to display offers at the right moments.

Custom fields: Apps for delivery date selection, gift messages, or custom order attributes. They collect information during checkout that shows up in your orders.

Trust and conversion: Trust badges, payment icons, urgency timers, and social proof. These extensions add conversion-focused elements without code.

Order validation: Apps that enforce business rules—age verification, address validation, fraud checks. Some use UI extensions for display, functions for enforcement.

Discounts and promotions: Advanced discount apps that go beyond native capabilities—stackable discounts, conditional free gifts, loyalty point redemption.

Installing checkout apps

1. Install the app from the Shopify App Store
2. The app requests permission to add checkout extensions
3. Configure the app’s settings
4. Use the Checkout Editor to position the extension’s blocks

Most apps handle the technical setup. You configure what to display and where.

Building custom extensions

For merchants with specific needs, custom checkout extensions are possible:

When custom makes sense:

• Unique business requirements no app covers
• Integration with proprietary systems
• Competitive advantage from differentiated checkout

What you need:

• Shopify Plus plan
• Developer with JavaScript/React experience (UI extensions) or Rust (Functions)
• Understanding of checkout extension targets and APIs

Development process:

1. Scaffold extension using Shopify CLI
2. Build extension logic and UI
3. Test in development store
4. Deploy via Shopify app
5. Configure via Checkout Editor

For most merchants, apps are more practical than custom development. The ecosystem covers most use cases.

Key targets and extension points

Checkout extensions render at specific “targets”—predefined locations in checkout:

Pre-checkout:

• purchase.checkout.actions.render-before — Before checkout begins

Information step:

• purchase.checkout.contact.render-after — After contact form
• purchase.checkout.delivery-address.render-after — After address

Shipping step:

• purchase.checkout.shipping-option-list.render-after — After shipping options

Payment step:

• purchase.checkout.payment-method-list.render-after — After payment methods

Order summary (sidebar):

• purchase.checkout.cart-line-list.render-after — After line items

Post-purchase:

• purchase.thank-you.block.render — Thank-you page
• customer-account.order-status.block.render — Order status page

Apps specify which targets they support. The Checkout Editor shows available extensions for each location.

The August 2026 deadline

Shopify set an August 28, 2026 deadline for checkout.liquid deprecation. If you’re on Plus and still using the old checkout.liquid customizations:

Before August 2026:

• Audit current checkout.liquid customizations
• Identify equivalent functionality in Checkout Extensibility
• Install apps or build custom extensions to replace functionality
• Test thoroughly in a development store
• Migrate to new checkout

What happens after:

• checkout.liquid stops working
• Customizations revert to default checkout
• Apps using deprecated APIs stop functioning

Most modern apps already use Checkout Extensibility. The risk is custom code written years ago for checkout.liquid.

Checkout Blocks app

For simple customizations without installing multiple apps, Shopify’s own Checkout Blocks app provides:

• Custom banners and text blocks
• Image blocks
• Order value limits (minimum/maximum cart totals)
• Basic upsells

It’s a good starting point before adding specialized apps.

When to upgrade to Plus for checkout

Consider Plus if you need:

• Custom checkout fields: Delivery instructions, gift messages, age verification
• In-checkout upsells: Offers displayed during the checkout flow
• Validation rules: Block checkout when business rules aren’t met
• Checkout branding: Full control over layout and design
• A/B testing: Test different checkout configurations

If you only need thank-you page customization or basic order follow-up, you might not need Plus. Thank-you and order status extensions work on all plans.

Practical recommendations

Starting out:

• Install Checkout Blocks for basic customization
• Add one upsell app if average order value matters
• Use trust badge apps if conversion is a concern

Growing stores:

• Layer multiple apps for different purposes
• Use the Checkout Editor to organize and position blocks
• Monitor checkout abandonment to identify friction

High-volume stores:

• Consider custom development for unique requirements
• Audit extension performance (too many can slow checkout)
• Build checkout profiles for different segments

The checkout extension ecosystem is mature. For most needs, apps exist. Custom development is for edge cases and competitive advantages.

Related guides:

• Shopify Plus vs Standard: Which order limit features require Plus?
• Best Shopify order limits apps (2026)