Shopify Checkout Extensions & Customization
Advanced Checkout Upgrades That Boost Conversions Without Compromising Platform Stability
Checkout UI Extensions, Post-Purchase Upsells, Custom Fields, Checkout Branding & Thank You Page - Built on Shopify's Modern Extensibility APIs, Safe for All Plans
We build Shopify Checkout Extensions that add conversion-boosting functionality to your checkout - post-purchase upsell widgets, custom delivery instruction fields, loyalty point redemption displays, trust badge sections, gift message inputs, and order protection offers - using Shopify's modern Checkout UI Extension APIs. These are React components running in Shopify's sandboxed extension environment, not checkout.liquid hacks that break on Shopify updates. The result: a more powerful, more personalised checkout experience that increases average order value and conversion rate - built to last, not built to break.
No checkout.liquid
NDA Protected
Free Consultation
100+
Checkout Extensions Built
12%
Avg. AOV Increase
100%
Checkout Stability (no breaks)
15+
Countries Served
What Are Shopify Checkout Extensions and Why Are They the Only Safe Way to Customize Checkout in 2026?
Shopify Checkout Extensions - officially called Checkout UI Extensions - are React components that add custom UI to the Shopify checkout flow by rendering in designated extension points within Shopify's checkout sandbox. Unlike the old checkout.liquid approach (which modified Shopify's checkout template directly and was Shopify Plus-only), Checkout Extensions work on all Shopify plans, run in a secure sandboxed environment that prevents buggy extension code from breaking the checkout for real customers, and are Shopify's only future-supported method of adding custom UI to the checkout, order confirmation, thank you, and order status pages.
Shopify deprecated checkout.liquid in August 2024. Any merchant still relying on checkout.liquid customizations is running deprecated infrastructure that Shopify will eventually stop supporting entirely. The migration path is Checkout UI Extensions - and the migration offers significant upgrades beyond just compliance. Extensions can render on the order confirmation (thank you) page and the order status page in addition to the checkout flow itself, enabling post-purchase upsell opportunities that checkout.liquid could not provide. Extensions work without Shopify Plus - so Standard plan merchants can now customize their checkout in ways that were previously Shopify Plus-exclusive features.
At Evolution Infosystem, Shopify Checkout Extensions are a specialist practice. Our team has built 100+ checkout extensions across the full extension point spectrum - checkout, cart, order confirmation, thank you page, and order status. We build post-purchase upsell widgets that average 8-15% additional revenue per order for merchants who implement them correctly, custom delivery instruction fields that reduce customer service queries by 20-30%, loyalty point redemption displays that increase loyalty program engagement, and checkout branding that makes the Shopify checkout feel like a native extension of the brand rather than a generic Shopify-hosted page.
What Checkout Extensions Can Add
- Post-purchase upsell widget (order confirmation)
- Custom delivery instruction text field
- Gift message input with optional wrapping toggle
- Loyalty points balance and redemption toggle
- Trust badge display (security, returns, certifications)
- Order protection upsell (insurance, extended warranty)
- Shipping date estimation display
- Custom consent checkbox (marketing, terms)
Checkout Extension Points - Where They Render
- checkout.contact.render-after - below email/phone field
- checkout.shipping-option-list.render-after - below shipping
- checkout.payment-method-list.render-after - below payment
- checkout.block.render - flexible block anywhere in checkout
- purchase.cart-line-item.render-after - below each cart item
- purchase.checkout.block.render - in checkout sidebar
- purchase.thank-you.block.render - order confirmation page
- customer-account.order-status.block.render - order status page
Our Shopify Checkout Extension & Customization Services
Evolution Infosystem covers the complete Shopify checkout extensibility spectrum - from single UI extensions to comprehensive checkout upgrade projects including branding, multiple extensions, post-purchase upsells, and thank you page customization.
Post-Purchase Upsell Extension
A React checkout extension rendering on the order confirmation page (purchase.thank-you.block.render) that displays a targeted product offer - selected based on what the customer just purchased - with a one-click Add to Order button using Shopify's applyCartLinesChange API. No re-entry of payment details. The upsell product and offer text are configured via a companion Shopify app Admin UI. Merchants implementing this extension average 8-15% additional revenue per completed order.
Custom Checkout Fields Extension
Adding custom input fields to the Shopify checkout for delivery-specific information - delivery instructions (gate codes, apartment access), gifting options (gift message, gift wrapping toggle, recipient name), business purchase fields (VAT/GST number, purchase order number), and custom preferences (installation appointment preferences, size confirmation, age verification). All field values are saved to Shopify Order note_attributes for fulfilment team access.
Loyalty Points Checkout Extension
Displaying a customer's loyalty points balance within the Shopify checkout and allowing one-click points redemption as a discount - using a Shopify Discount Function paired with a Checkout UI Extension. The extension reads the customer's points balance from your loyalty platform (Yotpo, Smile.io, LoyaltyLoop) via a backend API call and renders a toggle-style redemption UI in the checkout. Integrated with your loyalty program's redemption rules.
Checkout Branding API Customization
Applying brand-aligned visual styling to the Shopify checkout using the Checkout Branding API (available for all plans via the Admin API) - brand colours for buttons and accents, logo placement and sizing, custom corner radius for form elements and buttons, font selection from Shopify's supported font library, and background colour/image configuration. Checkout branding changes apply to the checkout, thank you page, and order status page consistently.
Trust & Social Proof Extension
Adding trust-building UI elements at key checkout abandonment points - trust badge display (secure payment icons, SSL badge, return policy icon) below the payment method section, social proof counter showing recent purchases, money-back guarantee banner, and certification/award display. Positioned using checkout.payment-method-list.render-after or checkout.block.render for optimal placement near the payment step where abandonment is highest.
Thank You Page & Order Status Customization
Extending the order confirmation (thank you) and order status pages with custom React extensions - referral program invitation, product review request widget, cross-sell recommendation, loyalty program enrollment CTA, next order discount code display, social sharing buttons, and brand story content. These pages have 100% open rate (every customer who completes a purchase sees them) - the highest-value real estate in your post-purchase experience.
Checkout Validation Extension
Adding client-side validation logic to the Shopify checkout - minimum order value enforcement with a clear message and cart editing shortcut, restricted product combination prevention, age verification checkbox for regulated products, geographic shipping restriction notices, and required custom field validation before payment. Validation extensions run before the customer proceeds to payment, preventing order issues that require manual intervention.
Checkout Extension + Shopify App Integration
Building Checkout Extensions as part of a broader Shopify public app - the extension reads and writes data to your app's backend API, allowing dynamic personalization based on customer data, integration with third-party services (loyalty platforms, insurance providers, warranty providers), and Admin UI configuration of what each extension displays. Billed through the Shopify Billing API as part of the app subscription.
Are You Leaving Revenue on the Table at Your Checkout?
Tell us your current checkout setup and conversion goals. We will show you exactly which extensions will move your AOV and conversion rate - with real numbers from similar merchants.
Why Choose Evolution Infosystem for Shopify Checkout Extensions?
Checkout is the highest-stakes page in your entire store. A bug on the homepage means a frustrated visitor. A bug in checkout means a lost sale - or worse, a customer whose payment is taken but order is not created correctly. Here is what makes our checkout extension practice different:
Shopify Extension APIs - No Hacks
We use only Shopify's official Checkout UI Extension APIs - no ScriptTag injection into the checkout DOM, no checkout.liquid modifications, no app proxy tricks. Official extension APIs are sandboxed, stable, and supported long-term by Shopify. Your checkout cannot be broken by our extension code even if the extension has a runtime error - Shopify's sandbox isolates it.
Extension Point Expertise
Shopify has 15+ extension points across checkout, cart, thank you, and order status pages. We know which extension points render where, which require Shopify Plus, which have rendering limitations, and which can access which Shopify APIs. This prevents the most common extension mistake: building an extension for an extension point that cannot do what the merchant needs it to do.
Performance - Extensions That Don't Slow Checkout
Checkout abandonment increases with every 100ms added to checkout loading time. We build extensions with minimal JavaScript bundle size, lazy-loaded API calls that do not block the checkout render, efficient React rendering patterns, and performance profiling before delivery. Your checkout loads as fast as or faster than without the extension.
Post-Purchase Revenue Optimization
The order confirmation page is the highest-converting real estate in e-commerce - customers who have just purchased have maximum trust and zero purchase friction (no payment re-entry). We design post-purchase extension UX specifically for this context: time-sensitive framing, minimal decision complexity, and one-click action. Average merchants implementing our post-purchase upsell extensions earn 8-15% additional revenue per completed order.
All Plans - Not Just Shopify Plus
checkout.liquid was Shopify Plus-only. Checkout UI Extensions work on all Shopify plans. If you are on the Basic, Shopify, or Advanced plan, you can customize your checkout with extensions - you do not need to be on Shopify Plus. We design extensions that work within the capabilities of your specific plan, and clearly advise when a Shopify Plus upgrade would unlock additional extension points.
Admin UI for Merchant Configuration
Every extension we build that requires merchant configuration comes with a companion Admin UI built with Polaris - so merchants can configure their extension settings (which product to upsell, what the trust badge text says, which loyalty program to connect) from their Shopify Admin without touching code. No hardcoded content.
Our Shopify Checkout Extension Technology Stack
| CATEGORY | TOOL 1 | TOOL 2 | TOOL 3 | TOOL 4 | TOOL 5 |
|---|---|---|---|---|---|
| Extension Framework | Checkout UI Extensions | @shopify/ui-extensions | @shopify/ui-extensions-react/checkout | Shopify CLI 3 | Extension DevServer |
| Language | TypeScript 5+ | React 18+ | JavaScript ES2024 | Shopify Polaris | - |
| Extension Points | checkout.block.render | purchase.thank-you.block.render | checkout.contact.render-after | purchase.cart-line-item | order-status.block.render |
| Checkout APIs | applyCartLinesChange | applyAttributeChange | applyDiscountCodeChange | useCartLines | useCustomer |
| Checkout Hooks | useApi | useSettings | useTranslations | useExtensionCapability | useSubscription |
| UI Components | Banner | BlockStack | Button | Image | Text / Heading |
| Also Used | InlineLayout | Divider | Icon | ChoiceList | TextField |
| Branding API | Checkout Branding API (GraphQL) | Admin API | Shopify CLI | colorSchemes | customFonts |
| Backend | Node.js + Fastify | Remix (Shopify CLI 3) | PostgreSQL (session + data) | Redis (cache) | Shopify Admin GraphQL |
| Loyalty Integration | Yotpo API | Smile.io API | LoyaltyLion API | Custom loyalty API | - |
| Testing | Shopify CLI (local preview) | React Testing Library | Jest | Playwright (post-install) | Shopify dev store |
| Performance | Lighthouse (checkout flow) | Bundle analyzer | React DevTools Profiler | Chrome Performance tab | Shopify checkout timing |
| CI/CD | GitHub Actions | Shopify CLI deploy | Semantic versioning | App version management | Fly.io / Railway |
Category
- TOOL 1Checkout UI Extensions
- TOOL 2@shopify/ui-extensions
- TOOL 3@shopify/ui-extensions-react/checkout
- TOOL 4Shopify CLI 3
- TOOL 5Extension DevServer
Our Checkout Extension Development Process - 5 Steps
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Checkout Extension Use Cases - What Each Type of Merchant Needs
D2C Brands
Post-purchase upsell, gift messaging, order protection
D2C brands benefit most from the post-purchase upsell extension - the order confirmation page has 100% engagement and zero payment friction, making it the highest-converting upsell opportunity in the entire customer journey. Gift message and gift wrapping extensions increase AOV for brands with high gift purchase rates. Order protection insurance upsell extensions generate additional revenue per transaction with minimal customer effort.
B2B & Wholesale Merchants
PO number, GST/VAT field, delivery notes, business name
B2B merchants frequently need custom checkout fields that standard Shopify checkout does not provide - purchase order number for accounts payable matching, GST registration number for tax invoice generation, company name for billing address, delivery window preferences, and site access instructions for business deliveries. Checkout validation extensions enforce minimum order values for wholesale customers.
Loyalty Program Merchants
Points balance display, redemption toggle, tier benefits
Merchants running loyalty programs (Yotpo, Smile.io, LoyaltyLoop) need the loyalty points balance displayed in checkout so customers are reminded of their points and motivated to redeem - driving repeat purchase. The extension reads the customer's balance via the loyalty platform API and renders a toggle for points redemption, applying the discount via a Shopify Discount Function when the customer opts in.
Subscription Merchants
Subscription upgrade prompt, auto-replenishment toggle
Subscription brands benefit from checkout extensions that prompt one-time purchase customers to switch to subscription - showing the per-unit savings of subscribing vs buying once. The extension reads whether the customer has chosen one-time or subscription purchase and, for one-time purchasers, displays a 'Switch to subscription and save X%' offer. This is one of the highest-ROI checkout extensions for brands with consumable products.
Food & Perishable Merchants
Delivery date picker, slot selection, dietary notes
Food and perishable product merchants need delivery-specific checkout fields - preferred delivery date (validated against available slots from a fulfillment calendar API), delivery window preference (morning/afternoon/evening), and special handling instructions (leave at door, refrigerate immediately, perishable products notice). These extensions reduce customer service queries about delivery preferences by 25-35%.
Premium & Luxury Brands
Checkout branding, complimentary gift wrapping, engraving
Premium brands need checkout branding that matches their store's visual identity - brand-aligned button colours, custom corner radius, header logo sizing, and background styling via the Checkout Branding API. Gift wrapping extensions with message personalization and premium packaging options are high-attachment for luxury product categories. Personalization extensions (engraving, monogramming, custom message) add both AOV and brand experience.
Still on checkout.liquid? Migrate before Shopify forces it.
We migrate all your existing checkout.liquid customizations to Checkout UI Extensions - with full feature parity and new Extension-only capabilities added as a bonus.
Want to see our checkout extension work?
Browse our checkout extension portfolio - post-purchase upsells, B2B custom fields, loyalty redemption, checkout branding.
Shopify Checkout Extensions We Have Built - Featured Projects
- Extension: purchase.thank-you.block.render
- Niche: Health
Post-Purchase Upsell - D2C Health Brand
Post-purchase upsell extension for a D2C health supplement brand - displaying a complementary product offer (product selected based on what was just purchased, via a simple product-to-recommendation mapping configured in Admin UI). One-click add-to-order using applyCartLinesChange. Admin UI for offer text, product selection, and discount percentage. A/B tested upsell copy over 3 months. Result: 11% upsell acceptance rate (industry average 5-8%), $4.80 average increase in AOV. Built with TypeScript, React, Checkout UI Extensions, Polaris Admin UI.
View Full Case Study- Extensions: contact.render-after + payment.render-after
- B2B
B2B Custom Fields - Industrial Supplier
Custom checkout fields for an industrial B2B Shopify store - Purchase Order number field (validated as alphanumeric, saved as order attribute for accounts payable reconciliation), GST registration number field (saved for tax invoice), and delivery site instructions (saved for logistics team). Fields built as Checkout UI Extensions using Shopify's TextField component, validated with useValidate, and saved via applyAttributeChange. Result: 28% reduction in post-order customer service queries about invoice and delivery details.
View Full Case Study- Extension: checkout.block.render + Discount Function
- Fashion
Loyalty Points Redemption - Fashion Brand
Loyalty points checkout extension for a fashion brand using LoyaltyLoop - displays customer's points balance in checkout and a toggle to redeem points as a discount. Extension reads balance from LoyaltyLoop API via app backend, renders using Shopify's ChoiceList component, and applies the discount using applyDiscountCodeChange when the customer toggles redemption on. Paired with a Discount Function that validates the redemption code server-side. Result: 34% increase in loyalty points redemption rate. 19% repeat purchase rate improvement in loyalty-enrolled customers.
View Full Case Study- Branding API + Extension: payment.render-after
- Luxury
Checkout Branding + Trust Badges - Premium Brand
Two-part checkout upgrade for a premium jewellery brand: (1) Checkout Branding API applied brand colour scheme (deep navy primary, gold accents), logo centred in header, large corner radius for premium feel - applied to checkout, thank you, and order status pages consistently. (2) Trust badge extension below payment methods showing hallmarked certification, free insurance, and 30-day return policy. Result: 8% checkout completion rate improvement. Average cart value at checkout increased 12% (fewer price-sensitive abandons). Branding built with Checkout Branding API GraphQL. Extension built with React + Checkout UI Extensions.
View Full Case Studycheckout.liquid vs Checkout UI Extensions - Complete Comparison 2026
Shopify deprecated checkout.liquid in August 2024. Here is everything you need to know about the difference and why migrating to Checkout Extensions is essential:
| FACTOR | |  |
|---|---|---|
| Status | Deprecated August 2024 - do not use | Fully supported - Shopify's official approach |
| Plan Requirement | Shopify Plus only | All plans (Basic, Shopify, Advanced, Plus) |
| Stability | Breaks on Shopify checkout updates | Sandboxed - cannot break checkout if extension errors |
| Future Support | None - Shopify will remove support | Long-term supported API with Shopify's commitment |
| UI Components | Any HTML/CSS (unconstrained) | Shopify's extension component library (consistent) |
| Extension Points | Entire checkout template | 15+ specific extension points |
| Performance Impact | Could significantly slow checkout | Minimal - extensions load asynchronously |
| GDPR / Privacy | Developer responsibility | Shopify handles compliance in sandbox context |
| Post-Purchase Pages | Not available | Thank you page + order status page |
| Checkout Branding | Full HTML/CSS control (Plus only) | Checkout Branding API (all plans) |
| Migration | Needs rebuild as UI Extensions | New development from scratch |
| Recommendation | Migrate away immediately | All new checkout work should use this |
IMPORTANT: If your store uses checkout.liquid customizations (script injection, custom HTML in checkout template), these are running on deprecated infrastructure. Shopify will remove checkout.liquid support. The migration to Checkout UI Extensions should be done proactively - before Shopify forces the change and you lose your customizations with no transition period. Evolution Infosystem migrates checkout.liquid customizations to Checkout UI Extensions as a standalone service, preserving all existing functionality and adding new Extension-only capabilities like post-purchase upsells.
Frequently Asked Questions - Shopify Checkout Extensions
Shopify Checkout Extensions (officially Checkout UI Extensions) are React components that render custom UI within Shopify's checkout flow, order confirmation page, and order status page - using Shopify's official extension APIs. They add functionality like post-purchase upsell widgets, custom form fields (delivery instructions, gift messages, PO numbers), loyalty points displays, trust badges, and subscription upgrade prompts. Checkout Extensions run in Shopify's sandboxed environment - meaning if an extension has a bug or error, it cannot break the checkout for customers, Shopify simply hides the extension. This makes them significantly more stable than the deprecated checkout.liquid approach. They work on all Shopify plans (not just Plus) and are Shopify's only supported method for checkout UI customization as of 2026.
checkout.liquid was Shopify's old checkout customization method - a Liquid template file that Shopify Plus merchants could modify directly to change the checkout HTML. Shopify deprecated checkout.liquid in August 2024 and it is no longer supported for new customizations. Checkout UI Extensions are the replacement - sandboxed React components that render in specific extension points within the checkout. Extensions are more stable (cannot break checkout), available to all plans (not just Plus), and support new capabilities including post-purchase extensions on the thank you and order status pages. Any store still using checkout.liquid customizations should migrate to Checkout UI Extensions to avoid losing those customizations when Shopify removes checkout.liquid support entirely.
Yes. Shopify Checkout Extensions allow post-purchase upsell widgets on the order confirmation (thank you) page using the purchase.thank-you.block.render extension point. The extension displays a product offer with an Accept button - when the customer clicks, the product is added to their order using Shopify's applyCartLinesChange API without re-entering payment details. The upsell product is configured by the merchant in the Shopify Admin. Post-purchase upsells are one of the highest-ROI checkout customizations - merchants implementing them average 8-15% additional revenue per completed order, because the customer is in maximum purchase intent state with zero payment friction.
Shopify Checkout Extensions are React components written in TypeScript that use Shopify's extension-specific hooks and UI component library. They are registered at specific extension points (render targets) using the reactExtension() function. Extensions access checkout data via hooks - useCartLines() for cart content, useCustomer() for customer data, useShippingAddress() for delivery address. They trigger checkout actions via mutation APIs - applyCartLinesChange() to add/remove products, applyAttributeChange() to save custom field values, applyDiscountCodeChange() to apply discount codes. They use Shopify's UI components (Banner, BlockStack, Button, Text, Image, InlineLayout) for rendering, ensuring visual consistency with the checkout without custom CSS. Merchant-configurable settings are read via useSettings().
Yes. Checkout UI Extensions work on all Shopify plans - Basic Shopify, Shopify, Advanced Shopify, and Shopify Plus. This is a significant improvement over checkout.liquid, which was Shopify Plus-only. However, some specific extension points and capabilities are restricted to Shopify Plus - for example, certain checkout branding customizations and some extension point locations have Plus-only restrictions. Evolution Infosystem assesses which requirements can be met on your current plan and clearly advises when upgrading to Shopify Plus would unlock additional capabilities.
The Shopify Checkout Branding API is a GraphQL API that applies visual styling to the Shopify checkout - button colours, corner radius, background colours, header alignment, font selection, and colour scheme configuration. Unlike checkout.liquid CSS (Plus-only, deprecated), the Checkout Branding API is available to all Shopify plans and applies styling through Shopify's official API in a structured way. Changes made via the Branding API apply consistently to the checkout, thank you page, and order status page. The API supports design tokens for colours and typography that map to Shopify's checkout component system - not arbitrary CSS that could break with Shopify updates.
Custom fields are added to the Shopify checkout using Checkout UI Extensions with the applyAttributeChange API. The extension renders a text input, dropdown, or checkbox at a checkout extension point using Shopify's TextField, Select, or Checkbox components. When the customer fills in the field and proceeds, the extension saves the value as an order attribute using applyAttributeChange - making it available in the Shopify Admin order detail, order confirmation email, and via the Admin API for fulfillment integration. Common custom fields include delivery instructions, gift messages, PO numbers for B2B, GST registration numbers, and installation preferences. All field values are validated client-side before the customer can proceed to payment.
Yes. Evolution Infosystem migrates checkout.liquid customizations to Checkout UI Extensions as a standalone service. The migration process starts with an audit of all existing checkout.liquid customizations - documenting every modification, identifying which can be replicated with Checkout Extensions and which require a different approach, and estimating the implementation scope. We then rebuild each customization as a proper Checkout UI Extension using React and Shopify's extension APIs. Some checkout.liquid customizations may require Shopify Functions to replicate the business logic, in addition to the UI Extension for display. We deliver the migration with feature parity plus any new Extension-only capabilities (post-purchase extensions, all-plan availability) as a bonus.
Checkout UI Extension development, post-purchase upsell extensions, custom checkout fields, loyalty points checkout extensions, checkout branding (Branding API), thank you page customization, order status page extensions, checkout validation, and checkout.liquid migration.
12% average increase in average order value across all post-purchase upsell extension projects - achieved through targeted product recommendations, A/B-tested upsell copy, and one-click add-to-order implementation.
Yes. Evolution Infosystem builds Checkout UI Extensions for all Shopify plans - Basic, Shopify, Advanced, and Plus. Extensions work on all plans. Specific Plus-only extension points are clearly identified in the requirements phase.
Yes. Evolution Infosystem uses only official Shopify Checkout UI Extension APIs - no ScriptTag injection, no DOM manipulation, no checkout.liquid. All extensions use @shopify/ui-extensions-react/checkout hooks and components for stability and Shopify review compliance.
Ready to Upgrade Your Shopify Checkout?
100+ extensions built. Post-purchase upsells. Custom fields. Loyalty redemption. Checkout branding. Yours next.