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Checkout extensibility

Checkout Extensibility

We customize the Shopify checkout the supported way — Checkout UI extensions, validation and Functions — so you can add fields, rules and logic without breaking upgrades or compliance.

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Overview

Checkout changes that survive updates

Shopify's checkout extensibility replaces the old checkout.liquid approach with supported extension points: Checkout UI extensions for the interface, Functions for validation and shipping or payment logic, and order attributes for capturing extra data.

Most of this lives on Shopify Plus. We're upfront about that: full checkout customization, branding APIs and delivery or payment Functions require a Plus plan. We scope to what your plan supports and build it so it survives Shopify's updates.

Discuss your project

Supported, not hacked

We use Shopify's official extension points, so customizations keep working through checkout updates instead of breaking.

Honest about limits

We tell you upfront which changes are Plus-only and which the checkout simply won't allow, before any work starts.

Conversion-minded

Every field, rule or upsell is weighed against checkout friction, not added just because it's possible.

What's included

What the engagement covers

Checkout UI extensions (custom fields & content)
Cart & checkout validation via Functions
Shipping & payment customization (Plus)
Order attributes & custom line-item data
Customer-specific and B2B checkout flows
Branding & checkout settings configuration

Technologies

  • Shopify Plus
  • Checkout UI extensions
  • Shopify Functions
  • GraphQL
  • Order attributes
  • TypeScript
Process

How we deliver

  1. Scope & feasibility

    We confirm what's possible on your plan, flag Plus-only or unsupported requests, and agree a realistic scope.

  2. Build extensions

    We build Checkout UI extensions and Functions in clean, documented code, tested against real checkout paths.

  3. Validate & QA

    End-to-end testing across customer types, shipping methods and payment options, plus edge-case validation.

  4. Deploy & support

    Controlled deployment with monitoring, plus documentation and post-launch support for your team.

Use cases

Where this helps most

Custom checkout fields

Capturing gift messages, PO numbers, delivery notes or tax IDs as order attributes at checkout.

Validation rules

Blocking or adjusting orders that fail rules — minimums, restricted regions, mixed-cart conditions — via Functions.

B2B checkout flows

Company-specific fields, terms and logic for wholesale customers within the standard checkout.

FAQ

Checkout Extensibility

Do I need Shopify Plus for checkout customization?
For most of it, yes. Full checkout UI customization, branding APIs and shipping or payment Functions require Shopify Plus. Some order-attribute and light extension work is more limited on non-Plus plans, and we'll confirm what applies to you.
What happened to checkout.liquid?
Shopify has moved merchants off checkout.liquid to checkout extensibility. We build only on the supported extension points, so your customizations don't break when Shopify updates the checkout.
Can you add upsells or custom logic at checkout?
Yes, within what the platform allows. We can add fields, content and validation via UI extensions and Functions. Anything Shopify doesn't expose an API for, we'll tell you honestly isn't possible.
Explore more

Related services

Shopify PlusAdvanced Shopify Plus builds — checkout extensibility, B2B and Markets.Custom Shopify AppsPrivate and custom apps that fit your workflows, not the other way around.Shopify CROTechnical CRO for Shopify — friction removed, experiments shipped, decisions from data.
Let's build

Ready to start with checkout extensibility?

Tell us about your store and your goals. We'll come back with a clear, honest plan and a transparent quote.

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Checkout Extensibility | EcomLabs