Checkout and accounts
Checkout Extensibility
Checkout Extensibility is how Shopify checkout is customised today: UI extensions placed at allowed points, Functions that change discounts, shipping or payments, and configuration in the editor. It replaces editing checkout.liquid, which is no longer an option.
Also called: checkout extensions, UI extensions, checkout customisation
The shift in thinking is this: checkout used to be a template you edited, and now it is an application you plug pieces into at specific places. You lose freedom and you gain the fact that a Shopify update does not break the store.
The three pieces
- UI extensions, which add content at allowed points of the checkout and the thank-you page: a notice, a field, a delivery information block.
- Functions, which change behaviour: discounts, validations that block payment, the order and availability of shipping and payment methods.
- The editor, for the visual side: logo, colours, fonts and block order, with no code.
What you can and cannot do
You can: warn about a minimum, show a B2B company’s payment terms, ask for a purchase order number, hide a shipping method, block checkout with a specific message.
You cannot: freely reorder checkout steps, inject arbitrary JavaScript into the page, or lay the checkout out like a normal page. If a quote assumes any of that, the quote is wrong.
The plan limit
The visual side and public apps work on plans without Plus. An extension or a Function written specifically for the store needs Shopify Plus, because it ships inside a custom app.
Documentation: Checkout Extensibility.