Define the purpose and location
Is the change about brand appearance, extra customer information or a rule affecting payment methods? Specify the audience and the example cart where it should apply.
A message in the theme cart is not an additional element on the payment page. Implementation depends on location, so clarify it before installing an app or commissioning development.
Branding through the checkout and accounts editor
Use checkout settings for basic changes such as logo, colours and fonts rather than editing the product template. Available design controls depend on Shopify’s current features.
Advanced branding through Checkout Blocks and the Checkout Branding API is intended for Plus. First check whether basic settings meet your needs. A programmed interface is not necessarily the starting point.
Understand UI extension availability
UI extensions add content at supported points. Extensions on information, shipping and payment pages require Plus. Certain thank-you and order-status extensions are available from Basic.
Installing an app does not remove these limits. Check where the advertised function appears. Checkout Blocks also offers different features by plan.
| Change | Basic and higher | Shopify Plus |
|---|---|---|
| Basic branding | Checkout settings | Checkout settings |
| Thank-you and order-status UI | Supported extensions available | Supported extensions available |
| Information, shipping and payment UI | Unavailable | Supported extensions available |
| Public-app Functions | Depends on Function and capability | Depends on Function and capability |
| Custom-app Functions | Unavailable | Available; check API-specific limits |
| Advanced branding | Limited | Additional Plus capabilities |
Business rules with Shopify Functions
Functions modify supported business logic such as certain discount, delivery and payment rules. They differ from visible UI blocks. Not every capability is available on every plan.
Public App Store apps containing Functions can serve non-Plus stores. A custom app containing Functions requires Plus. An existing public app may therefore be a different option from a bespoke single-merchant app. See Shopify app development.
Existing app or custom extension?
Compare existing apps against real cases. A “hide payment method” setting does not establish support for your combination of country, provider, customer and cart. Check pricing, access requirements and failure behaviour too.
Custom development fits a necessary unsupported process where the plan and platform allow it. Define a limited first scope. A separate ERP integration may provide data without asking customers for every detail during checkout.
Inventory existing customisations
List current apps, scripts and custom code. Older checkout.liquid instructions do not describe the current general extension approach. Preserve the business requirement and identify a supported implementation.
Remove existing functionality only after its replacement passes tests. Document dependencies on tracking, discounts, shipping and payments. For storefront pages, see theme customisation.
Acceptance tests for a checkout change
Go beyond a normal desktop purchase. Check addresses, carts and customer types. Accelerated payment journeys may behave differently from standard checkout; cover the paths you actually offer.
Agree who can disable the extension and how errors are detected. The change should behave sensibly if a connected service becomes unavailable.
- Realistic mobile and desktop purchases.
- Guest and signed-in customers where offered.
- Delivery countries and relevant payment methods.
- Discounts, gift cards, shipping thresholds and mixed carts.
- Accelerated checkout where offered and supported.
- Refunds and effects on invoices and accounting.
- Failure handling and return to previous behaviour.
